Screen Resolution on 21.5″ Mac

Hello

We have Dual Booting Imac enviroment.

When we boot into the windows enviroment and plug in the projector the resolution automatically goes to 640×480 and it greys out and cannot change it.

I have installed the latest drivers but still no joy.

If anyone has had this problem and has a fix or if anyone can shed any light with this i would be much appreciated.

Thanks

Scott