Bootup BSOD - CPU failure?

Problem:
Win7 Pro 64-bit installed and worked perfectly for a week. Then it began giving me the occasional random BSOD on bootup until it eventually stopped booting at all. I tried recovering from the Win7 install disk but it gives me the same BSOD. Here is where it occurs:

It boots from the disk and copies the files just fine


Then the progress bar moves for a short time


Then this:


Troubleshooting:
I ran several HDD tests (CHKDSK, Seatools, SpinRite 6) without a single error. I also tested the memory (memtest86 and windiag) but found no errors. I finally formatted the HDD for a fresh install and it still didn't work.

I reinstalled XP Pro 32-bit and it has been working flawlessly for six months.

Since then, I have systematically replaced the HDD, memory, DVD-ROM, PSU, and motherboard (going from a P35 to P45 chipset). I also tried three different video cards (1 ATI and 2 nVidia). The only thing I have not replaced is the CPU (e8400) because of the expense. None of these things fixed the problem.

When I try to install, I disconnect all the peripherals and internal components not necessary for installation. I've tried a PS/2 keyboard with no USB devices connected. I tried the backup disk I got from MS instead of the ISO I downloaded (which is what I used to install in the first place). I've flashed to the latest BIOS. I've played with every BIOS setting I can think of that might be causing the problem. None of this works.

Solutions?
The only hardware I haven't tested is the CPU. XP 32-bit works fine but Win7 64-bit does not. Is it possible that a CPU could fail in a way that it will not run a 64-bit OS but will still run a 32-bit OS?

It's got to be a hardware failure but I have never heard of a CPU acting this way. What else is there to try before replacing the CPU for an unlikely fix?

Original setup:
e8400
Gigabyte P35-DS4
4GB Corsair DDR2 800
Seagate Barracuda 250GB
Geforce 8800GT
Antec Truepower 550W

New setup:
e8400 (same one)
Gigabyte EP45-UD3P
4GB Patriot DDR2 1066
WD Black 500GB
Radeon 4890
Antec Truepower 750W

EDIT: added hard drives to setups

Have you tried resetting the bios. Sometimes bios corruptions due to weak batteries etc. can be the problem. There are two steps that you can take.
1) go into bios and set it to default.
2) reset the bios on the motherboard using jumpers and temporarily removing the bios battery.
If step 1 does not work, try step two.

here is a long shot and I am reaching. Windows XP will not access your 4 GB of RAM, however Windows 7 64 bit will access all the RAM. It is possible that you have a bad stick of memory that is ignored by Windows XP but comes into play with Windows 7. Try removing two sticks in different combinations and see if that makes a difference.

Another long shot-- have you tried underclocking your cpu or increasing your vcore and vdimm ?

Nope, I'll give those a try. But if installing Windows 7 means that I have to underclock my CPU, I'm going to be pissed.