Computer will not start!!

[Mosie100]

Hey everyone,
So basically, my computer is so messed up I have no idea what's wrong with it.
First, it'd be good to explain that I put a new CPU heatsink/fan (COOLER MASTER Hyper 212 Plus) onto the processor.
Now, for some reason, it just simply will not start. When I push the power switch, I only hear a slight click coming from the power supply. The motherboard light is showing up, I've taken out the power supply and it's working fine. I've taken everything out (besides the processor) and everything seems to be working.
One thing to note is that the heatsink was never firmly staying in place although it was clenched on (I was able to move it so it wasn't airtight).
Anyways, I'm thinking of just buying a new mobo/cpu and a new case as well cause my case is just all old.
Do we have any thoughts before I drop some cash down and re-make this rig?

Here's my rig all laid out in case we're wondering:
ASUS M4A785TD-V EVO AM3 MOBO
AMD Phenom II X4 955 3.2 GHz
Radeon HD 5850
8 GB ADATA Gaming Series DDR3 1600
OCZ 600W Power Supply


Thanks so much,
Mayberg

 

[Dangman]

Did you reseat the CPU?

 

[Mosie100]

Yeah I tried doing that and still no luck.

 

[Dangman]

Just to be clear: With the exception of the CPU, you have tested every other part in another PC?

 

[Mosie100]

Correct

 

[Hagrid]

Correct

Did you put the power supply on another computer and it worked, or did you just jumper it to see if it turned on?

Maybe take the MB out and test it outside the case? Maybe there is a short underneath.