Different USB - Windows needs admin rights to install - why?

On one of the laptops I use regularly my login doesn't have administrator rights. Whenever a different USB stick is plugged in Windows (XP) insists on doing some sort of driver install for which it requests administrator rights?

This seems to be the case for each and every USB stick that it's not seen before. It's a real nuisance.

Why does it need to install anything for each USB stick?

Most likely someone has installed something which has corrupted the contents of the catroot2 folder. Therefore windows isn't seeing the standard USB device driver as signed so asks for credentials to make it work.

I'd try method 2 and 3 suggested here to fix: http://support.microsoft.com/kb/822798

Or have a go at the MS fix it for me thingy.

Would that explain the fact that, under the administrator user (which I don't have access to), it all works fine?

Yes