Take a deep breath, and relax... (Not to quote Enigma, but...)
As CrazeD was talking about, remove all your items again. first:
- Make sure your power plugs are plugged in tightly to the mobo.
- reseat your ram, use only 1 stick for now. (just for testing, you can add the other later)
- if you hard drive is IDE make sure you have it set on CS (Cable Select) or Master if you only have 1 drive. If it's Sata, check your manual to make sure you plug it into the correct slot. This normally doesn't mater, but some mobo's require the first drive to be in a certain slot.
- recheck ALL your PSU connections for security
- lastly if all else fails, you might have a short in the mobo... which would require a rebuild from the start.