Help Me with my computer!!! Might make another giveaway ^_^

well thats quite vague m8 but you should maybe try scanning for spyware

When did the problem start
How often does it happen
can you send us a log of your processes

You've run antivirus/antimalware scans?

It could also be a bad PSU. I've had that happen. Have you recently added/upgraded anything? Try unplugging EVERYTHING from the PSU except the boot drive.

u may or may not be in for a long term headache with this problem.
a. take it to a store like compusa/tigerdirect/bestbuy to figure it out (risk them downloading all your porn to their hdd)
b. can you start in safe mode/ what was the last thing u did on the pc
c. time to debug the problem and disable certain parts to see if thats causing it
d. Find a way to back up you pc(possible with a windows installation disc, when u boot up and go to fix/repair u get a chance to go to windows explorer. Then back up all your stuff and reinstall windows after.
e.Record whats happening upload to youtube and post back here so we can see.

Run your PC in Safe Mode and run scans. Report anything here. Only thing is, I do not think it is software, I am leaning more towards hardware. Like annelions said, I think it is your PSU.