I originally posted this in the PSU/RAM support section, but I thought I'd try it here since a working PSU didn't fix the problem.
"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 tried starting it again with the paperclip but this time it went to a screen displaying information about my video card and just stayed there.
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.
I finally found the sticky on psu testing and it passed everything except this part of the continuity test: " Keeping one probe on chasis, use other probe to check the connectors non-black wires are non-zero (if a colored wire reading less than 50 suspect a problem)." Certain wires were reading 20-30 ohms, though I don't know what that means as far as the psu being good or bad goes.
I’m not with the computer right now, but here’s what I remember:
Intel Pentium 4 630 Prescott
ATI Radeon X300
675 watt Antec PSU(this original psu was replaced about 18 months ago when the fan inside started making a loud noise)
Edit: There were no diagnostic lights"
I was told flashing yellow light usually means a psu or mobo issue, does this mean it's most likely the motherboard? If so, how could the computer still start up?