Could of damaged it, but just to be sure- start from bare bones- just CPU, mobo, 1 stick of memory, video card, and keyboard. Start it up. See what it does, see how long you can stay in the BIOS if you can get that far.
After that, add hard drive, then mouse, then sound card, etc.
Also be sure the heat sink is firmly seated over that small raised area in the center of the CPU. If it's elevated on one half, it can still read "normal temps"... but overheating half the CPU causing it to lock up.
-SW