All you would need to know, in order to know what CPUs would fit it, is the model number of either the motherboard OR the prebuilt OEM number if it was purchased as a whole unit.
I would begin by double checking EVERY SINGLE ITEM at the following link. Don't skip anything just because you THINK you already know it's ok. Check everything. Reseat all memory modules. Make sure you installed the CPU the CORRECT way in the socket, and did not bend any pins. Likely, at a guess, I'd say that was the most probable mistake we see noobies make is trying to install the CPU the wrong way in the socket and bend the pins on the board or CPU all to hell.
Also, make sure you've reconnected the CPU fan, or it won't ever start and run unless the BIOS...