The mp3car.com forum has helped me enormously with my CarPC. Hopefully I can give something back...

After a full weekend and 1 day of vacation screwing around with the M7NCG 400 and the onboard IGP, not to mention constant cursing, sleepless nights, (plus a chipped patio door window), I figured out what was causing the instability issues (along with the inability to load windows) on my ver 7.2 M7NCG 400:

Make sure you are not using PC3200 DDR400 ram! Switch to PC2700!!

Why? Apparently the nForce2 chipset's IGP (on board graphics) only runs at 333 mHz and is known to be unstable with PC3200. I've read of a few people who were able to run the dual chaneel PC3200, but most weren't running the IGP. After a trip to Circuit City and the purchase of a 512mb Kingston Valueram PC2700, the XP installation issues ceased and I had a stable platform.

Also, make sure to read this thread:
Help: Biostar MB w/ Athlon XP 2500+ Mobile = crash
Why the hell this isn't a sticky is beyond me! For my particular setup (AMD Mobile Athlon 4 1.1GHz) I've got the frontside bus running at 200, with the multiplier set to 5. It shows up as a Mobile Athlon 1000MHz. Setting the multiplier to 5.5 causes the BIOS to recognize the chip as a standard Athlon. Underclocking isn't necessarily a bad thing... I believe the BIOS is setup for SPD for the RAM. Alternatively you can set the RAM to 83% (200 * 0.83 = 166MHz) which is the right setting for DDR 333 PC 2700.

Hopefully this saves someone a vacation day!