Hi, I installed USB Overdrive (a program), I clicked on restart and my iMac never got up. When I start it, the HDD and fans do work. But there is no boot sound, and when I change sound levels, I cannot hear it. I think, it never makes it to OSX. It does not load the OS. If there is anyone who knows the problem, please help. I dont think it is Graphics card (HD2600) failure. When I try to reset PRAM, nothing happens. Usually I must hear it restart again with loud boot sound but it never happens. Also my keyboard does not seem to work, as the CAPSLOCK button does not light up, when pressed. Edit: I changed RAM to different moduls, still the same. I checked the iMac RAM on a different computer, it works. Maybe USB Overdrive killed the USB slots? As my USB keyboard does not seem to work Thanks!