Preview window problems

[daveysue]

I'm a media teacher with 5 PCs in the classroom. All new, all hi spec but 2 of them have the same problem where after a few minutes work in VS8 the open file partially disappears behind the preview window making it impossible to save or open another folder.
Even closing the programme leaves the blackoutline of the preview window on the desk top and the only partial solution is to reboot where the same thing happens again.
I've upgraded to XP Service pack 2 - no solution, put on the latest Direct X with the same result. Any ideas people?
Ta
Dave