I have a Dimension 9100 running XP that won't turn on "normally", there is only a flashing yellow light when the computer is plugged on. After clearing the CMOS, checking cables etc., I tested the voltages on the psu with a multimeter, using a paperclip to short the green and ground, and everything was where it was supposed to be. I eventually was able to start the computer by shorting the green wire with a black one while the connector was plugged into the motherboard, this caused the computer to start up and continue running after I removed the paperclip. I restarted the computer, and it rebooted correctly. But when I shut it down, and tried to start it again with the power button, it didn’t turn on, the flashing yellow light returned. When I pressed the power button to turn it on that time, the fans and drives started for less than a second, then stopped. I also tried starting it with a good psu with no results. I found other people with the same problem who had said that broken USB ports in the front had caused the problem, so I replaced the front i/o panel with a new one with no results. The ports in front were broken, but the ones in back look okay visually. Intel Pentium 4 630 Prescott ATI Radeon X300 650 watt Antec PSU(this original psu was replaced about 18 months ago when the fan inside started making a loud noise) I don't know what it could be other than the mobo? But if so, how could the computer still start up and run fine like it did? Thank you!