PC won't boot

It all started when I didn't realize my reset button had actually gotten stuck in the depressed position. Because I didn't notice, I ended up holding down the power button by mistake. This caused my BIOS to reset, which is pretty standard behavior for my motherboard. The trouble really kicked in after I entered the BIOS and loaded my saved profile from slot 1 (that was literally the only thing I did before the system completely died on me). Now, after a restart, the BIOS won't even initialize. There’s no startup beep, the monitor shows no signal, the drives aren't spinning up, and the debug display just sits there at 8.8. before the whole thing restarts itself every 5 to 10 seconds...
I've already tried resetting the BIOS using the physical button and the jumper, and I even pulled the CMOS battery for a few minutes to clear everything out. I went through a whole process of elimination: I disconnected all three hard drives and the DVD drive, pulled both GPUs (the GeForce 8800 GTX) and tested them one by one, removed the Sound Blaster Xtreme, and tried every possible component combination. Eventually, I stripped it down to just the motherboard, CPU, and RAM. Nothing worked. The only thing I haven't tried yet is buying a brand-new battery to replace the current one, which I'm planning to do tomorrow. Does anyone have any other ideas on what I could try to get this machine running again?
My motherboard is an ASUS ROG Crosshair

So you're running two GeForce 8800 GTX cards...

Could it be a power supply issue?

It’s running on a 650W unit. I don't think it's an issue with the power supply itself, since it worked perfectly fine for years before suddenly just refusing to boot one day...

650W.

It doesn't matter what the wattage says if the unit itself is junk.

It can't be the power supply because it worked perfectly fine for years, and then suddenly, it just won't boot anymore.

That is exactly the point—especially if the unit is old (even if it is a big-name brand claiming to be a "true" 650W).

It could also be the motherboard.

There are just too many variables at play here—you really have to test things piece by piece, component by component, to pinpoint exactly where the failure is happening. Otherwise, there’s just no other way to go about it, unfortunately.

Timothy Kim60 said:It doesn't matter what the specs say if the quality is absolute crap.

That’s exactly my point—especially if we're talking about older units, even if they carry a big brand name and claim to be a "true" 650W...

There's also a chance the motherboard is the culprit here.

The Corsair power supply is fine. Honestly, I highly doubt the PSU just decided to die at the exact moment I loaded the Bank 1 settings in the BIOS. If it were actually underpowered, it would have struggled even after I disconnected all my hard drives and both graphics cards...

It’s the power supply. 99% chance.
Try a different unit or take the motherboard to a repair shop to test it against another PSU. Use a friend's setup if you have one.
Did you actually unplug the PC after hitting CMOS clear? Or did you just turn it off?
Are the fans spinning? That means you have 12V. Can you even measure the voltage? It shouldn't drop below 11.40V.
If the PSU is weak, you can measure the voltage. If it's dead, there's nothing left to measure.
Even a new power supply can fail; you never know. Yours is running hot and acting erratic because you have two GPUs inside that absolutely gorge on power. They are killing your PSU. I know those cards well.
Never forget: PSUs, HDDs, and SSDs wear out just like brakes on a car. It's inevitable.
The only solution is to buy a higher-wattage unit than you technically need. If it isn't running at full capacity, it has headroom and will last much longer—maybe even 15 years. Buy one that is 25-35% more powerful than required and you won't have to worry about it.