Maximum PC

Disregard the name. I learned html 4 way back when and the name stuck.

My "new" PC will only post if I reseat the CPU. The PC is "new" because I fell on hard times right after I bought several parts for a "cutting edge" i7 920 back in 2009. I recently puchased an i7 960, was given an old IDE hard drive, and borrowing a crappy Geforce MX 4000 PCI card.

The only things under warranty is my CPU, lifetime warranty OCZ ram, and 5 year PC Power & Cooling PSU.

Parts
Rosewill Case
PC P&C Sliencer 500w PSU
MSI x58 pro MOBO
Geforce MX 4000 PCI Card
OCZ DDR3 PC3-10666 Gold Low-Voltage Triple Channel OCZ3g1333lv6gk
WD something

Reseating with Arctic Silver 5 thermal paste
Stock Intel CPU cooler

When ever I reseat the CPU the computer will boot as much as I want for an hour or so but after that it just turns on with no post or beep.

Use canned air on the socket, and check for bent pins.

Is this the copper core stock cooler?

Yeah, the part of cooler touching the cpu is copper.

Good, that means you have the right cooler.

Instead of reseating the cpu next time just try draining the power. It seems like it's something else that is the problem and you messing with the cpu just happened to coincide with the PC working.