I have an intel socket 775 Intel Pentium 4 3.6ghz single core prossesor and i was trying to upgrade it to an Intel Pentium D 3.4ghz dual core Prossesor. Although when i put the new cpu in the system my computer wouldn't start the power light was on and the fans were running every thing seemed fine but all i had was a black screen, and yes the monitor was plugged in. so I took out the new cpu and put the old old back in and it worked just fine, oh and btw i was using HS compound the whole time as well. So i was wondering if maybe it is as simple as resetting the cmos settings? if someone could help that would be great.