can you part it out and see if anything works.....if not remove ALL extra items...try reseating memory )youd be suprised)? make sure video card is good! does the monitor respond (go from amber to green)? Are the fans spinning...? Did it ever beep...its there an internal speaker...is it connected?
There is a virus...dont see much of it latley called CHERNOBYOL or CHI that writes garbage to the bios at that point the hardware is usless but it is a rare case...
Good Luck