It's doubtful the video card and sound chip began failing at the same moment, right after you wiped out all the old software, so my bet is on the drivers. Check out ATI's website, as well as the computer manufacturer's for audio drivers, download, install, and restart. With a little luck that'll clear it right up.
Hope this helps,
John
Windows XP
1 gb ram
Pentium 4
Radeon 9800 XT video card - 256 mb
So I got a particularly nasty virus a week or so ago and was forced to reformat and reinstall everything. Now, though, some of the newer games I own cause the computer to crash - games which ran perfectly before I reinstalled, even while I had the adware virus.
the way in which they crash is this: the games in question (civ 4, Medieval II) run perfectly for a few minutes until the cursor freezes in place and a small black box appears beneath it. This lasts for a few seconds at which time the screen freaks out - it looks like tv static but its in the colors which were on screen when it froze. The speakers give out this nasty sound, like digital fingernails against a chalkboard, and the only way to shut down is to hold down the power button.
Everything else on the computer runs just fine. I have installed the latest driver for the video card (Catalyst Control Center) and am at a loss to what's causing this to happen. Older games don't have this effect on the machine, not sure what the problem is.
Overheating was suggested, so I cleaned out the inside of the cpu with compressed air, problem persists. If anyone has had this experience or has any idea as to the cause, i would REALLY appreciate it since I will not be able to afford a new machine for a long time ...
I also just installed direct x. that helped keep the programs running longer but the problem has not been fixed

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic