Hello! I just installed an old hard drive into a newly purchased pc. This pc is pre-built by a store near here which I trust fully (canada computers). After installing the old hard drive, the computer doesn't start. So I went backwards in my steps. I un-plugged the old hard drive, leaving the new hard drive with OS connected. Computer doesn't start... The start button blinks for a second and then nothing. No cpu fan movement, nothing. Next step was to un-plug the new hard drive and just boot without hard drives. It booted! yay! So I turned the computer off and re-plugged the hard drive. Same deal... It's a 500W PSU brand new so it should be able to handle both hard drives. So I un-plug the new hard drive again to see if it still boots. Nope... No more boot. Both hard drive un-plugged and the cd writer un-plugged. Still no boot... No power. No fan speed. Nothing. My last step is to try an other PSU on it. But I don't have one on hand. I'd need to un-plug the one in my computer. Any thoughts? I was properly grounded when I did the computer hardware changes. I just plugged in a hard drive (sata). I don't get it...