Hey, turns out the CPU was the problem. Thanks, man, you saved me a lot of time. I should have looked at that socket closer, and I would have seen the lock/unlock icon on there, lol.

I have a Dell Inspiron 1150 which had a problem with the plug (solder cracked through normal use). I bought a new part, desoldered the old one, soldered in the new one, and put everything back...