Ok,
Well what happened is I bought a used computer that was better then my moms....It was a desktop case, but the motherboard was compatible with my tower case. So I installed the used computers motherboard into my moms case and as soon as I plugged it in I got a spark sound and a puff of white smoke. I doubled check to make sure it wasn't a PSU problem and it wasn't. So i realized that I fried the mobo and I might as well install the old one back in the system. I put everything back the way it was except for the LEDS and SWITCH cables because i wasn't quite sure on where they go. So i knew where the power switch connector went so I put it in and turned on the computer, everything was working fine. Fans running, mobo lights flashing. But I wasn't getting a video signal.
So....after talking to my computer engineering teacher, he gave me some suggestions to try to see why it might not be working. Firstly the RAM. I checked every stick of RAM I had on a compatible computer to see if it was the Ram that might be causing the problem, but it wasn't. The second idea he gave me is that it might be the PSU. I told him that it was brand new and that it had worked before this incident, but he insisted that I check the voltages to see if they were correct. I was a little worried at first to check the voltages with a multimeter so i just put in another working PSU and nothing happened. So i eliminated that idea. I had an idea that the monitor might have been gone but i tested the monitor on different computers and it worked. Then there was the thought that it might be the video card, so i replaced it with another video card...same thing.....This computer did work before......
Well if anybody is still reading this, and has not giving up after reading my dilemma...please give me a hand..... If you need any info let me know....
Thanks