Keyboard issue

Hi,

Not sure if this is the right place for this but I couldn't find anywhere else to post it.

We have an Optiplex 755 running XP that intermittently changes the caps lock so it's reversed. All of a sudden in the middle of a sentence it suddenly becomes capital even though Caps lock is turned off and the shift button isn't being used. It does fix itself eventually but it can be difficult as it's the finance officer that it is happening to and she has a real issue when typing passwords.
We have tried numerous keyboards and updates but nothing has worked.
Any ideads would be appreciated.

Thanks

This might sound daft but i think there is a dell driver for keyboards on their site...