This happened to my sister's comp. By any chance did you ship it int the box that the case was shipped to you in? My sisters sloket, heatsink, modem and vid card were bouncing in her case when we got it that time. Luckily only the sloket was busted, but that was a pain to figure out, machine wouldn't boot at all. Put it all together and pray it works. If it doesn't remove everything but the motherboard, CPU, Vid card and your boot drives (get another floppy man). Try it then. Still doesn't work? Then either find a tech head friend who'll swap parts in his computer till you find the prob. If you know of a good computer shop (independent shops are better for this, they tend to have more people who know more about the hardware) go there and pay for an eval. They'll figure it out.