Artifacting and crashing on an 8800GT

Hey everyone:
I have a problem that I am unable to solve, and I am turning to you for help. Im running GeForce 8800GT with 512MB RAM and recently I've been having an artifacting and crashing problem. Thing is, the card has worked beautifully for more than 6 months and even more startling is that fact that older games are making it artifact and crash. Games like Far Cry and F.E.A.R. (Crysis however, will not crash even on the absolute highest I can get). I've used RivaTuner to crank my fan speeds up to 100% all the time and this seems to prolong playing time significantly, but it will crash at one point or another. The core temperatures don't get dangerously high under load (about 65C - 68C).

Could it be my graphics RAM overheating? These games weren't optomized to run at 1680 x 1050 which puts more stress on the video RAM. I tried running FEAR on a lower resolution and it still crashed. Even with the side panel off and a space fan blowing in the case, the game will crash at one point or another.

Could it also be CPU overheating? Is there a way to test?

Current setup (all stock cooling except for 100% graphics card fan speed and the space fan blowing in my case):
- Asus M2-N32 SLI Deluxe motherboard
- AMD Athlon X2 6400+
- Galaxy GeForce 8800GT 512MB
- 2GB (2 x 1GB) Kingston 667MHz
- 600w CoolerMaster power supply
- 500GB Seagate Barracuda 7200rpm

Thanks in advance.

Not in the immediate future. However, a friend of mine has the exact same card. Should I try swapping it in when i have the chance?

Even with more than 6 months of use without a problem?

anyone know how good www.ncix.com return policy is?
*very sad

MASSIVE PROBLEM:
I just remembered the "WARRANTY VOID IF REMOVED" sticker FELL OFF.
How screwed am I?

What if I were to, say, switch boxes and packaging with a friend and get the sticker on his card and put it on mine...
What are the odds of that working?

The box has the same serial as the sticker. Either that or the receipt should have the real serial number. I know this cuase when you buy a wifi card from frys they scan the serial number also so they know the right serial.