Ok, I downloaded Memtest86+. I let it install stuff to a floppy to boot from on restart, restarted, watched it do it's thing, went to work, came back, and it had frozen at 1:03:58 into it... I had to shut down the computer then cause it totally froze. On reboot (popped out the floppy) I ran Motherboard Monitor. My motherboard is not supported (Dell 8400)... it wasn't even on the list. THEN I installed SpeedFan... and I guess that I can't control the speed of my fans cause it doesn't even recognize them as existant (only Temp:"HD0 (160.0gb)"). But (a taste of hope) I decided to try HL2 again for the heck of it, and guess what... it lagged a little... but I got past that part, only for it to fully lag up again 10 minutes later (at the flaming wall you encounter on that fan-boat).
Thanx for the time in letting me know of these possibly great programs, but they did not solve my problem. If there is anyone who knows of a way to solve this annoying crash, please lend me a hand via posting... anything is worth my time if it might help.
PS. Perhaps "crash" is the wrong word. "Freezes" or "Hangs" would probably be more appropriate since the game just sits there repeating itself over and over again (audio-wise, the video freezes)