did you scan your pc with anti virus? some time virus can do this. some time After attach a keyboard, a mouse or another USB-based input device to your computer, your computer may no longer shut down correctly. For example, your computer may stop responding (hang) after you click Turn off or Restart. if this then try:
To work around this issue, disable power management of the USB hub.
Note If you perform the following procedure, your computer will be able to shut down correctly. However, this procedure may also reduce the battery life on a portable computer.
To disable power management on the USB hub:
1. Right-click My Computer, click Properties, click the Hardware tab, and then click Device Manager.
2. Double-click Universal Serial Bus controllers to expand it, right-click USB Root Hub, and then click Properties.
3. Click the Power Management tab.
4. Click to clear the Allow the computer to turn off this device to save power check box, and then click OK.
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