I've been looking for a answer to this but I couldn't begin to form a search right.... try googling windows unstable some time lol, don't get me wrong, win 7 is my jam...
the short story: bits of windows not drawn fully or blank white or black spots. sometimes bits of minimized windows left behind after minimizing.
The long story: I've seen this before when running unstable or high demand programs in the past but this system isn't too shabby with a fresh win7 install, amd x4 940 & gtx 275. I'm hoping nothing is wrong with the video card or anything. it seems to run pretty well, no issues in high power 3d. I even overclocked the ram and cpu and its still stable with without any additional problems and brought performance up in numbers (ran memtest, prime95)
hardware wise the 500w antec was a little underpowered for this setup I admit, It works stable but it put out more heat than I am comfortable with, it never hit OVP which is at 20a (18a rated). I added a additional psu to power all the fans and drives which brought my PSU temps down to a reasonable temperature.
the only corruption I see that's constant is there are L shaped 90 degree white lines bordering the temp readouts on speed fan, I tried reinstalling it and the video drivers. every so often I see the top of a menu bar left behind after I minimize a window such as firefox. sometimes parts of the task bar are blacked out/undrawn such as the clock area after running 3dmark vantage.