5x restart loop

[reboot]

I get to work on this computer, custom built (not by me) with an Asus A7V mobo (with ATA100 controller), AMD 1ghz chip, 256 SDRAM, WinME originally. One HD on the ATA100, and burner on IDE2 as slave.
At first glance I notice it's underclocked to 750mhz (100mhz FSB), and is overdue for a format/reinstall.
I reset the BIOS to 133mhz FSB to get the full 1ghz (is this the problem?) and it all seems to work fine.
The customer want's XP for multi-user security, no problem.
Fdisk, format, clean XP Pro install...
Now the computer goes into a restart loop when turned on cold.
Anywhere between 3 and 6 restarts (automatic restarts), and then it finally gets to the desktop and runs normally, no problems, nothing in device mangler, no IRQ's shared, ACPI is active, it all runs perfectly, once it finally gets there.
Fans all cleaned, temps are mid 70's on CPU and low 70's on Systemboard.
I haven't had a chance to look at the bootlog yet (later today).
Any clues how to fix/stop the auto-restart?

[Statica]

First thing to do would be to turn off autorestart on BSOD and get the error codes from the lockup.

Those temps seem awful high even for an Athlon especially for a sub 1Ghz CPU.

[reboot]

Yeah, I'll shut off the autorestart, but temps are cooler than the room it's in (73F)...should be no problem with it.
Any other ideas?

[Statica]

Err 70s as in Farenheit Sorry .. I thot you meant 70s Celsius

What sort of memory is the computer using? I know .. its the obvious one .. but that is usually the most likely cause of probs.

[reboot]

Thanks Statica.
I just got back from the client's house.
The machine runs perfectly at 750mhz (7.5x100), but will not run at 7.5x133.
Customer is returning it to the person that built it for some hardware fixing.
XP sure runs smooth on it though...too bad there's a hardware problem somewhere.
I have a feeling it's flaky RAM.