There's quite a couple of thing making a PC hang @ start up. What I sugest is to disconnect everything (USB, Hard Drive, CD Rom...), remove the RAM sticks, reset the mother board, re-install the RAM and try to boot it again. If it doesn't work... you may have faulty RAM, CPU or Mother board.

Also, make a visual inspection and Check if there's any "popped top" Electrolytic on the mother board.


HTH