NumLocker is free portable application that allows you lock state of Num Lock, Caps Lock and Scroll Lock keys. You can force these keys to "Always On" and "Always Off". NumLocker can help you prevent accidental pressing and changing state of there keys.
Just right-click on the tray icon and choose whether you want the key enabled or not, or you can set the key to be always disabled or enabled. NumLocker works with Windows 2000/XP/Vista/7 and starts automatically.