My friend was working on his computer and forgot to unplug the PSU and once he put his new sound card in he closed the case and he turned on his PC and it started for about a second then shut down and now it will not start at all. The green light on the mobo is on but nothing will even attempt to start, I made sure all the cords were in place and correctly plugged in which they were. I heard not unplugging your PSU when working on your computer can zap it on restart. My question is what gets zapped or broken, the mobo, the CPU, the PSU, the RAM, the harddrive or all? How can I test to see what he needs to replace considering nothing works. Thanks
Unfortunately with the PSU plugged in, power is going to the motherboard, as you've seen since you mentioned that the LED's on the motherboard are on. Firstly I would go through the checklist as jsc has said. Of course if any of the tips given involve removing hardware, be sure to unplug the PSU this time. Also one thing you may want to try that you haven't mentioned is removing the sound card that he installed, of course this time have the PSU unplugged.
I've not looked through the checklist that jsc has given you, and I'm not sure if it's in there or not, but you could try resetting the BIOS. Sometimes adding new hardware can cause the computer to not POST just because the hardware configuration has changed. Resetting the BIOS could help with this.