So the other day I leave for work, 6 hours later I come home and the computer is powered up but the monitor is blank, and nothing responds. I turn it off, and try to restart but nothing comes up on the screen and the thing begins to beep at me. The computer is an old HP vectra 400 or something like that, so I look up the the beep error codes in an online manual from HP and i find out that the 2 beeps i get means the power supply is in safe mode. I figured the comp either overheated, or some component died. I start pulling out pci cards and the vid card one at a time at try to boot to see if that works. After removing a couple things the comp seems to boot just fine. So I tell it to shutdown so I can start putting back in all the stuff I took out. It shuts down just fine, and I add in my soundcard I believe, and it wont boot again, same problem as before. I take out the sound card again, but this time same things as before happens. I switched out the PSU to see if that was causing problems, but no change. The odd thing is that as soon as the comp is plugged in, the power LED in the front lights up and stays on. Im at a loss as to what to do next. Anyone have any other ideas, or troubleshooting tips?