You don't say which Windows OS you are running but I believe it is almost the same for all versions so since it sounds like you may have had a driver crash then you need to boot into Safe Mode to trouble shoot and or fix the problem. To do this in Win7 use this info from the MS help site....
What is Safe mode?
http://windows.microsoft.com/en-US/windows7/what-is-safe-mode
To go into Safe Mode....
1. Remove all floppy disks, CDs, and DVDs from your computer, and then restart your computer. Click the Start button Picture of Start button, click the arrow next to the Shut Down button Picture of Shut Down button, and then click Restart.
2. Do one of the following:
* If your computer has a single operating system installed, press and hold the F8 key as your computer restarts. You need to press F8 before the Windows logo appears. If the Windows logo appears, you'll need to try again by waiting until the Windows logon prompt appears, and then shutting down and restarting your computer.
* If your computer has more than one operating system, use the arrow keys to highlight the operating system you want to start in safe mode, and then press F8.
3. On the Advanced Boot Options screen, use the arrow keys to highlight the safe mode option you want, and then press Enter. For more information about options, see Advanced startup options (including safe mode).
4. Log on to your computer with a user account that has administrator rights.
When your computer is in safe mode, you'll see the words Safe Mode in the corners of your monitor. To exit safe mode, restart your computer and let Windows start normally.
Hope this helps.
