Games keep minimizing to desktop.

I'm trying to do a little gaming at work during lunch and after (God knows I don't get an opportunity to at home anymore...grrrrr), but several games keep minimizing to desktop. These include Battlefield 1942, Enclave (will continuously do it, so you can't get to anything), and Vice City. Sometimes if you bring them back up often enough (it'll keep minimizing usually), they'll eventually run...and sometimes they crash out entirely. The refresh is only at 85hz max, which the monitor supports easily.

Others, like UT2k3 and RTCW_Enemy Territory run fine.

Any ideas?

The hardware:
AthlonXP 2800+
Asus A7N8X Deluxe
1gb Corsair pc3200
ATI Radeon 9700 Pro w/ Catalyst 3.2
onboard nForce sound.

Thanks!