OK, this is a crazy story and I had to share it. Maybe it's junk, maybe it'll be useful to someone.
First of all, my system:
ASUS M2N-E SLI Motherboard
AMD 4800+ Dual core AM2 CPU. Not overclocked (to my knowledge!)
2x1GB OCZ Gold DDR2 Ram
500GB WD SATA drive
OCZ 450W power supply
I took the plunge tonight and wiped my old WinXP system and went for a clean Windows 7 Ultimate install. I immediately hit upon problems. I'd get to the extracting files 0% during the first phase of install, and something random would happen. The machine would reboot. Or I'd get a BSOD indicating a fault. Or the screen would garble and the system would freeze. Or the mouse would freeze alltogether and I'd need to hard reboot the system.
I'd remembered trying to play around with Ubuntu on this particular machine last year and had some problems which I promptly forgot about. Uhoh.. I probably have some kind of hardware failure. Time to start checking components.
Firstly the system originally had three hard drives instead of the one, and I was concerned about power drain, so I pulled the power for these devices. No change.
Then I thought to check the memory. I ran memtest86+.. and the computer crashed before the first pass. Pulled one stick of ram... same. Replaced that stick with the other... and it worked! I let it go for two passes and no errors or crashing, so I thought: Problem solved, give OCZ a call on Monday, live with 1GB of RAM for a few weeks.
Windows 7 continued to crash during install at the same place.
I tried something suggested on these forums, installing in safe mode to turn off the nVidia driver. I was able to do this (it was tricky F8 timing) and did get further into the install process. But nVidia didn't show up in the installed devices and it crashed again on the second phase regardless.
I took a break, and let memtest run for another 5 passes. No errors.
I came back to the computer just now, looking to fiddle with BIOS settings. On a whim I turned off AMD's "Cool n' Quiet", the feature that turns down the fan RPM to get the system running.
Low and behold the system installed. First phase through fourth. No BSOD. No crashes. Windows Update ran, nVidia drivers installed. All seems well.. this minute. I stared at the screen in disbelief the whole time, waiting for a crash that didn't come.
Now there's no way in hell I'm going to reinstall to verify this was the reason for my problems. And this very well could crash tomorrow and I just fluked out in a 1 in 100 chance. But if someone with an AMD motherboard is having hellish problems with the install, try turning off Cool 'n Quiet and see if that helps out.