Sorry to interrupt milkmandan...
... but I'm breaking in my system with prime and memtest myself right now. One quick question to the crowd. Which version of memtest is everyone using? I've used one from memtest.org and one from memtest86.com. The .org version has a more recent version (Feb '08 vs. Dec '07), and recognizes the correct chipset and CPU series, but misreports the memory and CPU clock speeds. The one from .com is way off in everything (2.8GHz Pentium III?!). Is there another version out there that's more up to date and/or accurate?
So far, I have 400MHz FSB with 7.5 multiplier and all stock coolers. It's rock solid with prime95 on small FFT for 8 hours overnight in a hot garage (28-32°C). Worst-case temp was 72°C on core 0 (per speedfan), with others reporting between 65-70°C. I'll post a pic of the report tomorrow.
Next stop, some real cooling.