Can you help me with this problem?

What other Boot Disc's other than Hirens have you tried?

Also formating the HDD by no means means that it's clean and not infected many infections can survive a Format as the normal Format only writes to every third Sector of the HDD and a Fast Format does even less. If you want to be sure you need to run something like Boot & Nuke

http://www.dban.org/

or Kill Disc

http://www.killdisk.com/downloadfree.htm

To wipe the HDD. You should also test your HDD with it's makers Testing Utility which can be downloaded free from here

http://www.tacktech.com/display.cfm?ttid=287

But I personally would try a full Diagnostic Test with something like the Ultimate Boot CD and scan the entire system for problems. It's available free here

http://www.ultimatebootcd.com/download.html

To completely test your HDD you need to run the Makers Test and if it passes your OK but if it fails you need to remove the HDD fit to another computer and retest. If it passes the second Test the M'Board, Data Lead or Power Supply in your main computer is faulty and you need to test each item one at a time to find out and replace which is the faulty component.

if the Hirens Boot Disc works then you'll also get The Ultimate Boot CD to work as it works exactly the same way as Hirens. ;)

Col

un-overclocking your CPU?

I have seen OC CPU's do what you are describing.