Windows Stability + Overclock, heat related?

[$ineX]

I'm running an Iwill KA266-R with a 1ghz athlon @ 1.33Ghz. It runs fine and at good temps but I'm running into windows stability issues. Are there any ways to correct this? This expecially occurs inside 3d applications. ie. Tribes 2, Quake 3, UT but it completes 3dmark2001 every time without fail.
(at 4223 with a radeon =). Anybody have any ideas on how to correct this.
Or, what version of windows will run without producing errors.

[Thelemac]

Sounds like a video card problem. Is that oced at all? You might need some cooling on that...

[Hoot]

What are your temps (ambient and cpu)? What core and i/o voltages? These are important to know if we are to give opinions.

Hoot