My keyboard and mouse were working just fine yesterday, then today they are not working when I get to the start-up page. I am using Windows XP Professional. When I plug other USB devices, they can draw power from the PC with no problem.
Do they work in safe mode (F8), or other user?
Try a system restore. (start >run>msconfig>launch system restore. Choose a date before the problem happened.
Check if event viewer caught anything.
If this is a laptop, try removing the battery and run only on cable.
Also U can try, remove cable and battery, hold down power button for 30 seconds or more, then put back and see if keyboard/mouse are working.
U might still need to check Bios settings related to Keyboard, mouse (usb stuff)