Windows 7 : How to Use System Restore, How to Troubleshoot USB Problems

10/8/2012 7:19:23 PM

1. How to Use System Restore

System Restore regularly captures system settings so that you can restore them later if you experience a problem. Using System Restore to return your computer to an earlier state should be one of your last troubleshooting steps, however, because it might cause problems with recently installed applications and hardware.

You can run System Restore from within either the System Recovery tools or from within Windows. To use System Restore from System Recovery tools (which is necessary only if Windows will not start). To use System Restore from within Windows, follow these steps:

  1. Click Start, click All Programs, click Accessories, click System Tools, and then click System Restore. The System Restore Wizard appears.

  2. If this is the first time you are running the System Restore Wizard, click Next to accept the default restore point. Then, skip to step 4.

  3. If you have run System Restore previously and it did not solve the problem, click Choose A Different Restore Point and then click Next.

  4. On the Restore Your Computer To The State It Was In Before The Selected Event page, select the most recent restore point when the computer was functioning correctly. Click Next.

  5. On the Confirm Your Restore Point page, click Finish. When prompted, click Yes.

  6. System Restore restarts your computer. When the restart has completed, System Restore displays a dialog box to confirm that the restoration was successful. Click Close.

If System Restore does not solve your problem, you can do one of two things:

  • Undo the system restore The problem might not be the result of changes to your computer at all, but rather a hardware failure. Therefore, using System Restore might not solve your problem. Because restoring the computer to an earlier state might remove important changes to your system configuration, you should undo any restorations that do not solve your problem. To undo a system restore, simply rerun System Restore using the steps in this section and choose the default settings.

  • Restore an earlier restore point Your problem may be caused by recent changes to your computer, but the negative changes occurred before the most recent system restore. Therefore, restoring an earlier restore point might solve your problem. Repeat the steps in this section to restore to an earlier restore point.

2. How to Troubleshoot USB Problems

The most common way to connect external devices to a computer is USB. USB provides expandability without the complexity of connecting internal devices such as PCI cards. Connecting USB devices is so simple that most users can connect and configure USB devices without help from the Support Center (provided that they have sufficient privileges). However, users do occasionally experience problems with USB devices. The following sections provide guidance for troubleshooting USB problems.

2.1. How to Solve USB Driver and Hardware Problems

If you do experience problems, following these steps might solve them:

  1. Restart the computer. Some software might require the computer to be restarted before functioning properly. Additionally, restarting the computer forces Windows to detect the USB hardware again.

  2. Install updated driver software, if available. Check Windows Update and the hardware manufacturer's Web site for updates.

  3. Uninstall the device's driver and software, disconnect the USB device, restart the computer, and then follow the manufacturer's instructions to reinstall the software. Many USB devices require a driver. Typically, the driver should be installed before connecting the USB device. If you are experiencing problems with a USB device, the most likely cause is a driver problem. For information on how to troubleshoot the driver problem. External storage devices such as USB flash drives and external hard drives typically do not require a driver, because the required software is built into Windows.

  4. Disconnect the USB device and reconnect it to a different USB port. This can cause Windows to detect the device as new and reinstall required drivers. Additionally, this will solve problems related to a specific USB port, such as a failed port or power limitations.

  5. Replace the USB cable with a new cable or a different cable that you know works properly.

2.2. Understanding USB Limitations

If you installed the USB device's software correctly and you are using the most up-to-date version of the driver, you still might have problems because of USB's physical limitations. Limitations that can cause problems include:

  • Insufficient power Many USB devices receive power from the USB port. Connecting too many unpowered devices to a USB hub can result in a power shortage, which can cause a USB device to not respond properly. This is particularly common when using an unpowered external USB hub. To quickly determine whether a problem is power related, disconnect other USB devices and connect each USB device directly to the computer one by one. If devices work when connected separately but fail when connected simultaneously, the problem is probably power related. Decrease the number of devices or add a powered USB hub.

  • Excessive length USB devices can be no more than 5 meters (16 feet) away from the USB hub to which they are connected. Although USB devices will never ship with cables longer than 5 meters (16 feet), some users connect USB extenders to allow longer distances. Depending on the quality of the cable and possible sources of interference, you might experience problems with shorter distances. To determine whether length is the source of problems, remove any USB extenders and connect the USB device directly to the computer.

  • Too many devices USB can support up to a maximum of 127 devices connected to a single USB host controller, which is more than enough for the vast majority of client computer scenarios. You can have a maximum of seven layers of USB hubs connected to the computer's USB host controller, and no more than five external hubs.

  • Insufficient bandwidth Most USB devices are designed to work within USB bandwidth limitations. However, video cameras in particular might need more bandwidth than USB is capable of providing. If you receive a "Bandwidth Exceeded" message, first try disconnecting other USB devices. If the message continues to appear, attempt to reduce the bandwidth used by the device by lowering the resolution of the camera. For best results with a video camera, connect it to an IEEE 1394 (also known as Firewire or iLink) port.


If you see the message, "Hi-speed USB device is plugged into non-hi-speed USB hub," the USB device is USB 2.0, but the USB port is an earlier version. The device will probably work, but it will work slowly. You can improve performance by adding a USB 2.0 port to the computer.

2.3. How to Identify USB Problems Using Performance Monitor

If you are concerned that you may have a USB bandwidth or performance problem, you can identify the problem by using the Performance snap-in:

  1. If the problem you need to identify occurs when you are actively using a USB device, connect the USB device that you want to troubleshoot and turn it on. If the problem occurs when you first connect the USB device, do not connect the device until after you have begun logging.

  2. Click Start, right-click Computer, and then select Manage.

  3. Expand System Tools, Performance, Monitoring Tools, and then click Performance Monitor.

  4. On the Performance Monitor toolbar, click the green Add button.

  5. In the Add Counters dialog box, in the Available Counters group, expand USB. If you are troubleshooting the failure of a USB device, add the following counters for the <All Instances> instance:

    • Iso Packet Errors/Sec

    • Transfer Errors/Sec

    If you are troubleshooting a USB performance problem, add the following counters for the <All Instances> instance:

    • Bulk Bytes/Sec

    • Avg. Bytes/Transfer

  6. Click OK to add the counters to Performance Monitor.

Performance Monitor begins collecting data about your USB devices and connections. Attempt to reproduce the problem (for example, by copying a file to a USB hard disk or connecting a video camera). If you are troubleshooting performance problems, right-click the Performance Monitor display and click Clear immediately after you begin using the device to ensure the counters include only data created during your test. The longer you allow the test to run, the more accurate it will be. You should stop Performance Monitor before your test ends.

After reproducing the problem, pause Performance Monitor by clicking the Freeze Display button on the toolbar or by pressing Ctrl+F. Because you added performance counters for all instances, you probably have a large number of counters. To browse individual counters to identify the specific source of your problems, press Ctrl+H to enable highlighting.

Click the first counter in the list. After you select a counter, the graph related to that counter will be shown in bold. Examine the values for that particular counter. If the counter shows an error, make note of the USB controller and device causing the problem. Press the down arrow on your keyboard to select the next counter and continue analyzing USB performance values.

USB errors should not occur under normal circumstances; however, Windows can automatically recover from many USB errors without affecting the user. 

If you are troubleshooting USB performance problems, examine the Bulk Bytes/Sec counter to identify the instance that relates to the device you are using. Then select the counter and make note of the Average value. Theoretically, USB 2.0 can transfer a maximum of 60,000,000 bytes/sec. However, this theoretical maximum will never be realized. More realistically, you might be able to achieve half that value. USB storage devices are often much slower, and performance will vary depending on the performance of the device itself. USB hard disks typically average less than 10,000,000 bytes/sec but can peak over 20,000,000 bytes/sec. Performance of hard disks will also vary depending on the portion of the disk being written to or read from, the size of the files being accessed, and the disk fragmentation. 

2.4. How to Examine USB Hubs

Connecting a USB device to a computer can include several different layers:

  • A USB host controller, which is connected directly to your computer USB host controllers are often built into the computer's motherboard, but you can add them by using an internal adapter or a PC card. If the name of the controller includes the word "Enhanced," the controller supports USB 2.0.

  • A USB root hub, which is connected directly to the USB host controller Typically, USB root hubs are built into the same device that contains the USB host controller—your computer's motherboard or an adapter card.

  • Optionally, additional USB hubs that connect to the USB root hub to create additional USB ports USB hubs can be external devices that you add, they can be an internal device within a computer, or they can be built into a docking station.

You can use Device Manager to examine the USB controllers and hubs in a computer, determine their power capabilities, and examine the power requirements of the connected devices. This can help you to identify the source of a USB problem. To examine USB devices, follow these steps:

  1. Click Start, right-click Computer, and then select Manage.

  2. In the Computer Management console, click Device Manager (under System Tools).

  3. In the right pane, expand Universal Serial Bus Controllers.

  4. Right-click an instance of USB Root Hub (there might be several) and then click Properties.

  5. Click the Power tab, as shown in Figure 1. This tab displays the power capabilities of the hub and the power requirements of every connected device. To determine the requirements of any specific device, disconnect the devices and connect them again one by one.

Figure 1. View USB root hub properties to determine power capabilities and requirements.

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