Locking up in in Opengl games...

I lock up in opengl games…
Mainly Quake 3 and HalfLife…/can pass a benchmark in all plus 3dmark…
What’s weird is that after 10 minutes or so of online gaming, I freeze up…/sometimes I can play for 1 hour or so…
No heat issues at all…
No IRQ conflicts…
No new software, off a fresh format…

My current specs:
/a blast from the past…

Gateway g6-450/only altered with sound card and CLAP DDR…

p2 450
440bx tabor 2/onboard sound, and that crap…/bypassed…
384 sram, pc100(3 sticks of 128)
CLAP DDR (not o/c now), 4,47 detenators
Win98 1st edition
mx300 aureal drivers (happens in or out)
Intell 2100 modem
350 watt power supply
DX8, happened with7 also…

Sorry for the issue…

hope people can help?