Why would my computer all of sudden reset clock, show new boot screen, and run fans loud?

BIOS resetting is a certainty. And since you didn't do it manually(choosing to reset the BIOS in the BIOS!), you should replace the CMOS battery with a new one.

That doesn't explain CPU temp being high.

Enable Q-fan in the BIOS. Q-fan may just be an ASUS thing, but you have an ASUS board.

Then at least the fans should quieten down even before the going into windows stage. It'll be interesting if they then speed up again and how soon.

You do need to address the CPU overheating.

You could open the computer and check that the CPU fan is spinning fast.. And check the temp immediately on booting windows. And check the temp in the BIOS if the BIOS shows CPU temp..

And if you're not worried about static possibly damaging a part(I'd risk it on my comp for sure, and on somebody elses with a warning to them so getting an ok first!), then feel the heatsink and see if it is very hot. It could be misreporting the temp. Maybe there are other ways of viewing or measuring the temp of the cores.

A few months ago, it started to not boot unless I removed my USB headphones connected to a USB hub, everything else worked fine.

Maybe this would cure the booting problem...

I'm assuming you don't want to boot from a USB device normally, so the easiest way to solve this is probably just to disable your system's USB boot capability in your BIOS. It may be listed as "Boot from USB" or "Boot from external device" depending on your motherboard ... but whichever it is, if it's set to "enable", try disabling it and see if that solves the problem. You may also want to check your boot device priority in the BIOS -- make sure Hard Drive is set to first, CD/DVD to second, and anything else either third or not at all.

http://www.tomshardware.com/forum/275674-31-system-boot