GeForce 2 Pro, XP Pro, OpenGL Lockup/Video Garble

In games like Quake III: Arena, MOHAA, Tribes 2 and Half-Life (any mod, in OpenGL mode), my computer will randomly lock-up mid-gameplay and the screen will turn to a garbled mess of flickering lines. Ctrl-Alt-Delete sometimes works, but most of the time I have to hard-reset the computer via the tower case button. I have used the 21.83 nVidia reference drivers, 23.11 reference, 23.12 (via Windows Update), 21.83 from Leadtek’s website and the leaked 27.42 nVidia drivers ( Every version of the drivers has caused the same problem. I have also updated my chipset drivers from Intel to the latest version to no avail, as well as checking for sound card drivers. I have read through Leadtek’s FAQ and all the settings listed that I could change in my BIOS are correct, and I have tried setting my AGP Arpeture to 1, 1/2, and 1/4 of my system RAM. I can NOT modify the AGP speed from 4x in either my BIOS or via the ‘PowerStrip’ utility.

Disabling ‘OpenGL Extensions’ in Quake 3 prevents the lockup from occurring as far as I can tell (it may just delay it) at a severe cost in FPS and image quality (no reflections, etc.) Please help! System specs below:

Intel Pentium 4 @ 1.8 GHz
Gigabyte P4-Titan GA-8ITXE
Leadtek GeForce 2 Pro w/ 64MB DDR-RAM (AGP 4x)
Creative Labs Sound Blaster Live! Platinum w/ Live!Drive 1
D-Link DFE-530TX+ 10/100BaseT
IBM-DPTA-372050 20.0 GB ATA/66 HD
CompactFlash reader on LPT1 (pass-through to Canon BJC-5000)
Brother HL-1250 Laser Printer on USB
Yamaha CRW8824E
Microsoft Windows XP Professional (all Windows Updates installed)