Fu#$ Windows

So Half Life 2 is coming out in a few days and i can be more pissed off. What, you say, it can't be so. Well the problem is not with calflife, its with my computer, presumably the windows XP operating system on it. So for a while now i have been having some graphics troubles with first person shooters and other 3d rendered games. UT 2004, Jediknight outcast, Rainbow Six 3......ect but not games like warcraft 3 or starcraft or generals, some of which are also 3d rendered. Basicly the textrues are repeatedly disapearing and reappearing. walls and objects flash in and out of existance. Sometimes the game freezes for up to 10 seconds and then continues on as normal, still with texture glitches. On rare occations when the game starts working again the floor or the models have all disapeared or turned invisable is a better description.

Stepts to fix problem:

1. I first touhgt it was driver problem but no i have the newest driver.
2. Then i thought windows had a glitch. i had been running for almost a year without a reinstall so i formatted and started from scratch. That did not work either.
3. so i had installed some new ram recently, the nvidia web site sait theat may be the culperit. I downloaded some memory testing software and it found no problems.
4. NVIDIA says i sould test my CPU, havent done that yet but i dont expect that to be the culperate.
5. so now i am left with 3 possabilities. My video card is screwed, NVIDIA does not support the gForce 4 anymore or Windows Service Pack 2 (also installed around the same time as my new ram). You can guess which one i suspect.

If anyone has any ideas, here are my system specs
-AMD Athalon XP 2100+
-512 MB Ram (333 Mhz)
- NVIDIA gForce 4 MX 400
- Soundblaster Live 5.1
- Windows XP with Service pack 2 (not for much longer)