Problem with ATi 9200 and Steam CounterStrike 1.6

When I am playing Counter Strike using Steam and I hit Alt-Tab to go back to windows for whatever reason sometimes my whole computer freezes should I have VPU disabled and if I have it disabled sometimes I am able to get it going again if I can get the mouse to click back open the Counter Strike tab on the taskbar.

The screen goes black and comes back and I am able to move the mouse some and then it freezes go black and comes back......

but most of the time if I can get Counter Strike back open there is no more problems.....

if i have VPU disabled it just plain crashes and Locks up everything and I have to reboot by manually hitting the restart button.

I am just wondering if anyone else has had this problem.