1. Try to go into BIOS using keyboard. Does it allow you to enter BIOS? Does keyboard work in BIOS?
2. The best way you could solve this is by elimination. Try mouse/keyboard in different PC. If they work they are obviously not the issue. If this is the case or, - If keyboard works in BIOS but not in Windows, - try what I suggested earlier - try repairing or reinstalling the system. Helps to have a Windows Repair disk or Windows installation media handy.