Btw, I am a novice with these types of problems, but I hope I was helpful. You might want to wait till someone who knows what they're doing. Sorry.
I'm worse than a novice. I know just enough to screw things up. I am considering new vid cards, but want to hold off on that purchase for a few months.

When did you install Service Pack 3? Have these games worked since you installed it?
That is a good question, but since I've had this problem for several months I can't really remenber. I do remember that COH's worked fine one evening; then the very next day it would not.

Did you do anything specific leading up to the errors? Did it start out random and get progressively worse? The MS KB article would lead one to think it's a hardware error. When was the last time you cleaned out your PC real well, blew out all the dust and gunk?
The only thing I can remember changing was to update the vid drivers. I noticed with the original driver that I would get occasional slow downs,freezes, weird colors etc...and sometimes when right in the middle of doing whatever (from playing games to web browsing) the screen would freeze, black out, and the pc would reboot. There would be a cryptic message pop up during this reboot stating that your system has recovered from a fatal error, but wouldn't give anymore info than that. This went on for several weeks on an infrequent basis, but most of the time these games played ok. Then one day, we no play for you. I figured updating the vid driver would solve this, but it hasn't, though I haven't experienced the reboot or recovery from fatal error message since. I also noticed that there are a few faint veritical red & blue pixels, like a dotted line on the borders of the web pages I'm viewing.

I vacuum off the air intakes on the case every couple of months, but have not opened it up and cleaned the inside, so I guess I'll give that a try.

Thanks for the replies.