What happened to my PC?

Doctor Detroit

Everything seems to be working, but nothing is.

Started out having some issues with my wifi adapter dropping. Thought it might be the adapter so I upgraded it.

Then the install couldn't find the new one, but Windows found wireless networks. But the keyboard couldn't type the password. So I rebooted.

And now we're hanging on the boot.
CPU is there.
USB controllers initialized.
It says the RAM is OK.
...and that's it.

I haven't been inside in a while, so I'm guessing something died of old age.

Any suggestions?

EDIT: I got it into Windows. But it's slow. I think it might be the HDD.

LD50

My first guess is that the mobo is failing. It could also be your PSU, but my money is on the mobo. You should do some basic troubleshooting and see if we can narrow things down:

Unplug everything that isn't essential:
Remove the video card, disconnect all drives and peripherals, remove all but one ram stick (leave the one stick in the socket closest to the cpu).

See if it can boot into the bios. If it does, it's probably not the mobo, if it doesn't it probably is.