you probably picked up the case and it slid in. I know I always have screws sliding around my caseThermite Paste said:the dumbest thing ive ever done was probably this:
when i was building a pc, i accidentally got a screw stuck in the power supply (have no clue how it got in there) and when i turned it on, a bigass spark flew out of the back, and all of the electricity in my upper level just shut off. i had to go buy a new power supply, and a dissection of the old one revealed what had happened.