1. Applications and the Registry
The Registry is perhaps Windows Vista’s most important component
because it stores thousands of settings that Windows needs. The Registry
is important for your applications, as well, because most Windows
applications use the Registry to store configuration data and other
settings.
When you install an application, it typically makes a half-dozen different Registry modifications:
Program Settings
Program
settings are related to the application as a whole: where it was
installed, the serial number, and so on. The program settings are placed
in a new subkey of HKEY_LOCAL_MACHINE\Software:
HKLM\Software\Company\Product\Version
Here, Company is the name of the program vendor, Product is the name of the software, and Version is the version number of the program. Here’s an example for Office 2007:
HKLM\Software\Microsoft\Office\12.0
User Settings
User settings are user-specific entries, such as
the user’s name, preferences and options the user has selected, and so
on. The user settings are stored in a subkey of HKEY_CURRENT_USER\Software:
HKCU\Software\Company\Product
File Types
File types refer to the file extensions used by
the program’s documents. These extensions are associated with the
program’s executable file so that double-clicking a document loads the
program and displays the document. The extensions and file types are
stored as subkeys within HKEY_CLASSES_ROOT.
If the application comes with OLE (object linking and embedding) support, it will have a unique class ID, which will be stored as a subkey within HKEY_CLASSES_ROOT\CLSID.
Application-Specific Paths
In computing, a path
is a listing of the folders that the operating system must traverse to
get to a particular file. Windows Vista uses a variation on this theme
called application-specific paths.
The idea is that if you enter only the primary name of a program’s
executable file in the Run dialog box (press Windows Logo+R), Windows
Vista will find and run the program. For example, WordPad’s executable
file is Wordpad.exe, so you type wordpad in the Run dialog box, click OK, and WordPad opens.
Note
A file’s primary name is the part of the filename to the left of the dot (.). For example, the primary name of the file Excel.exe is excel.
Windows
finds the program because the application’s executable file is
associated with the particular path to the folder in which the file
resides. These application-specific paths are set up in the following
key:
HKLM\Software\Microsoft\Windows\CurrentVersion\App Paths
Each application that supports this feature adds a subkey that uses the name of the application’s executable file (for example, Wordpad.exe). Within that subkey, the value of the Default
setting is the full pathname (drive, folder, and filename) of the
executable file. Note, too, that many applications also create a Path setting that specifies a default folder for the application.
2. Understanding Application Compatibility
Most new software
programs are certified as Windows Vista–compatible, meaning that they
can be installed and run without mishap on any Windows Vista system. But
what about older programs that were coded before Windows Vista was
released? They can be a bit more problematic. Because Windows Vista is
based on the code for Windows 2000—which was in turn based on Windows
NT—programs that are compatible with those operating systems will
probably (although not definitely) be compatible with Windows Vista. But
the real problems lie with programs written for Windows 9x and Me.
Windows Vista—even Windows Vista Home—uses a completely different code
base than the old consumer versions of Windows, so it’s inevitable that
some of those legacy programs will either be unstable while running
under Windows Vista or they won’t run at all.
Why do such incompatibilities arise? One common
reason is that the programmers of a legacy application hardwired certain
data into the program’s code. For example, installation programs often
poll the operating system for its version number. If an application is
designed for, say, Windows 95, the programmers might have set things up
so that the application installs if and only if the operating system
returns the Windows 95 version number. The program might run perfectly
well under any later version of Windows, but this simplistic brain-dead
version check prevents it from even installing on anything but Windows
95.
Another reason incompatibilities arise is that calls to API
(application programming interface) functions return unexpected
results. For example, the programmers of an old application might have
assumed that the FAT (file allocation
table) file system would always be the standard, so when checking for
free disk space before installing the program, they’d expect to receive a
number that is 2GB or less (the maximum size of a FAT partition).
However, FAT32 and NTFS (NT file
system) partitions can be considerably larger than 2GB, so a call to the
API function that returns the amount of free space on a partition could
return a number that blows out a memory buffer and crashes the
installation program.
These types of problems might make it seem as
though getting older programs to run under Windows Vista would be a
nightmare. Fortunately, that’s not usually true because the Windows
Vista programmers did something very smart: Because many of these
application incompatibilities are predictable, they gave Windows Vista
the capability to make allowances for them and so enable many older
programs to run under Windows Vista without modification. In Windows
Vista, application compatibility
refers to a set of concepts and technologies that enable the operating
system to adjust its settings or behavior to compensate for the
shortcomings of legacy programs. This section shows you how to work with
Windows Vista’s application compatibility tools.
Caution
Although application compatibility can work wonders to give aging programs new life under Vista, it doesn’t mean that every
legacy program will benefit. If history is any guide, some programs
simply will not run under Vista, no matter which compatibility rabbits
you pull out of Vista’s hat. In some of these cases you may be able to
get a program to run by installing a patch from the manufacturer, so
check the program’s website to see if updates are available that make
the program Vista-friendly.
Determining Whether a Program Is Compatible with Windows Vista
One way to determine whether an application is
compatible with Windows Vista is to go ahead and install it. If the
program is not compatible with Windows Vista, you might see a dialog box
similar to the one shown in Figure 1.
At this point you could click Run Program (in
some dialog boxes, the button is named Continue), but this is a risky
strategy because you can’t be sure how the program will interact with
Windows Vista. This approach is riskiest of all when dealing with disk
utilities, backup software, antivirus programs, and other software that
requires low-level control of the system. It’s extremely unlikely that
Windows Vista would ever allow such programs to run, but you should
always upgrade such products to Windows Vista–compatible versions. A
much safer route is to click Cancel to abort the installation and then
visit the vendor’s website or the Windows Update site to see whether a
Windows Vista–friendly update is available. (You can often get the
company’s web address by clicking the Details button.)
Note
Where does the information in these dialog boxes come from? In the %SystemRoot%\AppPatch folder, Windows Vista has various system database (.sdb) files that contain messages such as the one shown in Figure 5.5 for all known applications that don’t have compatibility fixes (discussed later in this section). The system database
files aren’t text files, so opening them with Notepad or WordPad will
not allow you to read any of these stored messages.
A better approach is to find out in advance
whether the program is compatible with Windows Vista. The most obvious
way to do this is to look for the Designed for Windows Vista logo on the
box. For older programs, check the manufacturer’s website to see
whether the company tells you that the program can be run under Windows
Vista or if an upgrade is available. Alternatively, Microsoft has a web
page that enables you to search on the name of a program or manufacturer
to find out compatibility information: http://www.microsoft.com/windows/catalog/.
What if you’re upgrading to Windows Vista and
you want to know whether your installed software is compatible? The
easiest way to find out is to use the Upgrade Advisor tool, which is
available on the Windows Vista Professional CD. (The Windows Vista Home
CD doesn’t have the Upgrade Advisor.) Insert the Windows Vista Pro CD
and, when the Welcome to Microsoft Windows Vista screen appears, click
Check System Compatibility. Run through the Advisor’s dialog boxes until
you get to the report on system compatibility. This report will list
software that doesn’t support Windows Vista and possibly software that
needs to be reinstalled after the Windows Vista setup has finished.
Understanding Compatibility Mode
To help you run programs under Windows Vista,
especially those programs that worked properly in a previous version of
Windows, Windows Vista offers a new way to run applications using compatibility layers. This means that Windows Vista runs the program by doing one or both of the following:
Running the program in a compatibility mode—
This involves emulating the behavior of previous version of Windows.
Windows Vista can emulate the behavior of Windows 95, Windows 98,
Windows Me, Windows NT 4.0 with Service Pack 5, and Windows 2000, as
well as two more versions that are new to Windows Vista: Windows 2003
with Service Pack 1 and Windows XP with Service Pack 2.
Temporarily changing the system’s visual display so that it’s compatible with the program—
There are five possibilities here: setting the color depth to 256
colors, changing the screen resolution to 640×480, disabling Windows
Vista’s visual themes, disabling desktop composition, and disabling
displaying scaling on high-DPI settings. Note that the last two settings
are new to Windows Vista.
Note
Windows Vista and Microsoft often use the terms compatibility layer and compatibility mode
interchangeably, depending on which compatibility tool you’re using. In
some cases, the emulations of previous Windows versions are called operating system modes.
These
are the broad compatibility layers that Windows Vista supports. As
you’ll see a bit later, Windows Vista also offers fine-tuned control
over these and other compatibility settings. For now, however, to set up
a compatibility layer, you right-click the program’s executable file or
a shortcut to the file, click Properties, and then display the
Compatibility tab in the property sheet that appears. To set the
compatibility mode, activate the Run this Program in Compatibility Mode
For check box (see Figure 2),
and then use the list to choose the Windows version the program
requires. You can also use the check boxes in the Display Settings group
to adjust the video mode that Windows Vista will switch to when you use
the program.
Scripting Compatibility Layers
What do you do if you have a batch file that
needs to run one or more programs within a temporary compatibility
layer? You can handle this by using the following command within the
batch file before you start the program:
SET __COMPAT_LAYER=[!]layer1 [layer2 ...]
Here, layer1 and layer2 are codes that represent the compatibility layers. Table 1 lists the 16 codes you can use.
Table 1. Codes to Use When Scripting Compatibility Layers
| Code | Compatibility Layer |
|---|
| Win95 | Windows 95 |
| Win98 | Windows 98 / Windows Me |
| Win2000 | Windows 2000 |
| NTSP5 | Windows NT 4.0 SP 5 |
| WinXPSp2 | Windows XP (Service Pack 2) |
| WinSrv03Sp1 | Windows Server 2003 (Service Pack 1) |
| 256Color | 256 color |
| 640×480 | 640×480 screen resolution |
| DisableThemes | Disable visual themes |
| DisableDWM | Disable desktop composition |
| HighDpiAware | Disable display scaling on high DPI settings |
| RunAsAdmin | Run this program as an administrator |
| International | This layer handles incompatibilities caused by double-byte character sets |
| LUA | Limited User Access—This
layer redirects some Registry and file operations to nonrestricted
areas for users that don’t have permission to access restricted areas
(such as the HKLM key)
|
| LUACleanup | Limited User Access Cleanup—This layer removes the Registry settings and files that were redirected using the LUA layer |
| ProfilesSetup | Profile Setup Support—This
layer is used for older programs that install only for the current
user; the layer ensures that the program is installed for all users |
If you’ve already applied one or more layers to
the program using the techniques from the previous section, you can tell
Windows Vista not to use one of those layers by preceding its keyword
with the ! symbol. Also, to turn off the compatibility layers, run the
command without any parameters, like so:
For example, the following commands set the
compatibility layers to Windows 95 and 256 colors, run a program, and
then remove the layers:
SET __COMPAT_LAYER=Win95 256Color
D:\Legacy\oldapp.exe
SET __COMPAT_LAYER=
Note
The compatibility layers created by SET __COMPAT_LAYER apply also to any processes that the affected application spawns. For example, if you set the Windows 95 layer for Setup.exe, the same layer will also apply to any other executable called by Setup.exe. You can find more information about the SET __COMPAT_LAYER command and its parameters at http://support.microsoft.com/default.aspx?scid=kb;en-us;286705.
Note
When you execute a program using a
compatibility layer, Windows Vista creates an environment within which
the program can function properly. For example, a program running under
the Win95 layer actually believes that Windows 95 is the
operating system. Windows Vista accomplishes that not only by returning
the Windows 95 version number when the program calls the GetVersion or GetVersionEx
API functions, but also by “fixing” other incompatibilities between
Windows 95 and Windows Vista. For example, Windows 95 programs expect
components such as Calculator and Solitaire to be in the %SystemRoot% folder, but in Windows Vista these are in the %SystemRoot%\System32\ folder. The Win95 layer intercepts such file calls and reroutes them to the appropriate location.
The Win95 layer consists of dozens of
such fixes, which are part of a large database of incompatibilities
maintained by Microsoft. As of this writing, hundreds of
incompatibilities have been identified, and others might be found in the
future. To get access to all these fixes and so get fine-tuned control
over the compatibility issues relating to any legacy program, you need
to use Application Compatibility Toolkit (ACT). Download and install the
latest version of ACT (version 5.0 was in beta testing as of this
writing) from the following Microsoft web page: go.microsoft.com/fwlink/?LinkID=36665
