Help, My systems won't boot

[ComputerLiterate]

I've recently replaced my heat sink fan inside my computer after doing so, my PC has refused to boot, It wont even connect with the monitor, at first i booted and the fans would all work but now it restarts after about 4 seconds.

I need to solve this problem, but I'm unsure of what the problems is, go easy I'm new.

 

[cmichael138]

Possibly somethig was dislodged/disconnected during the fan switch. So it turns on, with no signal on the monitor, then shuts off after 4 seconds?