My overclocking run didn't last very long.  That friggen thing ran so damned hot and I don't have temps from the overclock saved anywhere that I can remember.  Windows would run fine with that OC but the stress testing apps would come up with errors all the time.  It's kinda dumb because my P5B board killed itself while I was trying to find settings that would get me near 4GHz without errors in orthos or occt - i forget.  No way was I going to run it 24/7 on air though and the mobo was RMA'd and got a new one just fine :)

http://www.ocbase.com/perestroika_en/ - OCCT
http://www.overclockingwiki.org/index.php?title=Overclocking_software_tools
http://www.tomshardware.com/reviews/dual-41-ghz-cores,1253.html - Tom's Hardware did it first - I got mine for $60 @ newegg in early 2007.