Heatsink too tight?

[DBest]

I have a PC here that wont POST.

Soo i checked the usual stuff, then when it came to the cpu testing. after reseating the cpu then resting the heatsink on top it starts. so after putting the heatsink back on it wont start. i did this several times, and everytime the heatsink is put back properly on it wont start, but just resting it on top it starts.

I dont want to buy a new motherboard. How can this be fixed ? any ideas

[Moondog]

What type of fastening system is used? Could the force on the cpu be uneven, or something may be shorting out?

[DBest]

its using a stock intel cooler. the one with the the 2 tabs you have to turn to tighten it.
i don't know if anything is shorting out.
I've shaved some plastic off to reduce the fastening tension, still no luck.