You can use the BCD Editor to add, modify, and delete
entries in the BCD data store. Although I discuss related tasks in the
sections that follow, only experienced users should attempt to modify the
BCD data store. If you make a mistake, your computer may end up in a
nonbootable state.1. Changing the Default Operating System
To change the default operating system entry, you can use
the /Default parameter for BCDEdit. The syntax for this parameter
is:
Bcdedit /default bootldrid
where bootldrid is the GUID of the boot
loader to use. You can boot to a particular installation of Windows 7 or
a later Windows operating system by specifying the identifier for the
related boot loader. When you view verbose details for the BCD data
store, the identifiers for a particular Windows Boot Loader are listed
with its entry, such as:
Windows Boot Loader
-------------------
identifier {1cafd2e9-e035-11dd-bbf6-bdebeb67615f}
device partition=C:
path \Windows\system32\winload.exe
description Windows 7
locale en-US
inherit {6efb52bf-1766-41db-a6b3-0ee5eff72bd7}
recoverysequence {1cafd2f0-e035-11dd-bbf6-bdebeb67615f}
recoveryenabled Yes
osdevice partition=C:
systemroot \Windows
resumeobject {1cafd2e8-e035-11dd-bbf6-bdebeb67615f}
nx OptIn
quietboot No
debug No
ems No
The Windows Boot Manager entries also list each Windows
Vista or later operating system by its identifier in the displayorder field:
Windows Boot Manager
--------------------
identifier {9dea862c-5cdd-4e70-acc1-f32b344d4795}
device partition=L:
description Windows Boot Manager
locale en-US
inherit {7ea2e1ac-2e61-4728-aaa3-896d9d0a9f0e}
default {1cafd2e9-e035-11dd-bbf6-bdebeb67615f}
resumeobject {1cafd2e8-e035-11dd-bbf6-bdebeb67615f}
displayorder {1cafd2ed-e035-11dd-bbf6-bdebeb67615f}
{1cafd2e9-e035-11dd-bbf6-bdebeb67615f}
{360a7720-e6ef-11dc-89b8-84b5c301f2c8}
toolsdisplayorder {b2721d73-1db4-4c62-bf78-c548a880142d}
timeout 30
You could set one of the related operating systems as the default
for the computer, as shown in this example:
bcdedit /default {1cafd2e9-e035-11dd-bbf6-bdebeb67615f}
If you want to use a pre–Windows 7 operating system as the
default, you’d use the identifier for the Windows Legacy OS Loader. The
related BCD entry looks like this:
Windows Legacy OS Loader
------------------------
identifier {466f5a88-0af2-4f76-9038-095b170dc21c}
device partition=C:
path \ntldr
description Earlier Version of Windows
Following this, you could set Ntldr as the default by entering:
bcdedit /default {466f5a88-0af2-4f76-9038-095b170dc21c}
2. Changing the Default Timeout
You can change the timeout value associated with the
default operating system using the /timeout parameter. Set the /timeout parameter to the desired wait time in
seconds, such as:
bcdedit /timeout 30
If you set the timeout to zero seconds, the system will boot
automatically to the default operating system.
3. Enabling Physical Address Expansion
PAE is a feature that allows x86-based computers to
support more than 4 GB of physical memory, effectively expanding the
number of addressable bits from 32 to 36. Physical memory in addresses
above the first 32 bits is accessed as regular 4 KB memory pages.
NOTE
You do not need to enable PAE on a computer running a 64-bit
version of Windows, as 64-bit Windows can access more than 4 GB of
memory automatically.
If you want to enable PAE through the BCD, you can use the command
syntax:
bcdedit /set bootldrid pae paeState
where bootldrid is the identifier for
the operating system that should use PAE and
paeState specifies how you want PAE to be
used:
- Default
If you set paeState to Default, the operating system will use
the default configuration for PAE.
- ForceEnable
If you set paeState to ForceEnable, the operating system will
use PAE.
- ForceDisable
If you set paeState to ForceDisable, the operating system will
not use PAE.
This means you could enable PAE for the operating system
identified by this boot loader identifier:
Windows Boot Loader
-------------------
identifier {0c728e1b-d009-11da-b18b-9dc1d02cdda0}
using the following command:
bcdedit /set {0c728e1b-d009-11da-b18b-9dc1d02cdda0} pae forceenable
4. Changing the Operating System Display Order
You can change the display order of boot managers
associated with a particular Windows 7 or later operating system using
the /Displayorder parameter. Follow
the parameter with the operating system identifiers in the desired
display order.
Thus you could change the display order of the operating systems
identified in these BCD entries:
Windows Boot Loader
-------------------
identifier {0c728e1b-d009-11da-b18b-9dc1d02cdda0}
Windows Boot Loader
-------------------
identifier {263bf496-4ab4-11db-b478-c0671802252f}
using the following command:
bcdedit /displayorder {263bf496-4ab4-11db-b478-c0671802252f}
{0c728e1b-d009-11da-b18b-9dc1d02cdda0}
You can set a particular operating system as the first entry by
using /addfirst with /displayorder, such as:
bcdedit /displayorder {263bf496-4ab4-11db-b478-c0671802252f} /addfirst
You can set a particular operating system as the last entry by
using /addlast with /displayorder, such as:
bcdedit /displayorder {263bf496-4ab4-11db-b478-c0671802252f} /addlast
5. Changing the Restart Boot Sequence
If you’d like to boot to a particular operating system one
time and then revert to the default boot order, you can use the /bootsequence parameter to do this. Follow the
parameter with the operating system to which you want to boot after
restarting the computer, such
as:
bcdedit /bootsequence {0c728e1b-d009-11da-b18b-9dc1d02cdda0}
Now when you restart the computer, the computer will set the
specified operating system as the default for that restart only. If you
restart the computer again, the computer will use the default boot
order.
