Come on man, we're talking about a motherboard heatsink that got dislodged somehow, not opening mysterious email attachments. It either got bumped hard in transit and is just now having the problems and/or the build quality on the motherboard was a little shoddy to being with. There's not a lot of wiggle room as to what else would cause that.
What I had in mind saying this, is that you may have treated the PC without needed precaution, like dropping it accidentally when moving etc. - and I didn't mean "opening mysterious email attachments", because it's not a problem with software . Also, if you put together the PC yourself, you may be doing something wrong. Next time I recommend you ask someone to do it for you.