PC sometimes fails to boot

Hopefully, someone here can help with this problem.

I am running an older Dell XPS 700.

Basic specs:
Dual CPU Intel Pentium 4 3.8GHz
Windows XP Pro (SP3)

Basically, when powering on, all fans would spin, then everything would shut down after a couple of seconds. It never lasted long enough for the monitor to even display anything. (It would show "on" lights for a second, then display "Power Save Mode", then the PC would just quit working.

I replaced (and upgraded) the power supply. At that point, I could get it to almost boot (BIOS loads, Windows begins to start), but then the monitor would go into to power save even while the fans were still spinning and the computer sounded as if it was still running. I disconnected the dual graphics cards one at a time and eventually found one was bad. The computer will boot and run with just 1 of the 2 cards in. I did have to boot to the Windows disk in order to repair some files, but was able to get the PC running. It will run absolutely fine, Windows can auto-update and auto-restart with no issues. I can manually reboot with no issues.

HOWEVER, sometimes, after shutting down, the computer is hard to get running from a cold start. I can power it on, all fans spin up, Windows starts booting, etc. But then it will shut down. Sometimes, it completely powers off. Other times, the fans continue to spin and all components seem to be running, but the monitor goes into power save and shows no activity. It can take several attempts to get it to completely boot.

Once it has booted, however, it runs without any issues. I can leave it on for days with no problems, even when Windows updates and restarts. I can can restart myself with no issues. The only time I have trouble is when I try to start it up from a "cold" state.

For instance, today the electric company replaced our meters without warning and shut off power long enough that even the UPS failed, so when I got home, there was a notice on the door and the PC had been down who knows how long. I had to attempt to boot it 6 times before it would run. Once it's up, no problems.

What could cause this intermittent issue? Power supply is good, fans are good, RAM checks out OK, no viruses/Windows issues.

Could it be the other graphics card? (I wonder due to everything seeming to still run with no display, and it's NOT the monitor.) If the card is bad, why would it work ok once started, and not while trying to start? Previous experience with failing cards has led me to expect performance issues like graphical glitches during gaming which I am not experiencing at this time. Would 2 cards AND the power supply fail at the same time? Could a failing power supply screw up both cards?

There were definite power supply issues before replacing. It would not run with everything disconnected. It would try to start, but immediately shut down (within 5 second). After a shut-down, the only way to get it to even try to start again was to disconnect the power cable from the power supply, then replug it in (hitting the power button did nothing). All fans spin once computer tries to start.

I'm obviously savvy enough to pull and switch graphics cards, test fans, disconnect auxiliary devices, and to replace my power supply. But I'm not THAT savvy with hardware. Any help is appreciated, but beyond the basic unplugging and replugging in, I will need some pretty detailed instructions on how to accomplish anything more complicated. I'm willing to give it a try though, as the computer is out of warranty anyway, and Dell is NO help at all. I refuse to pay to talk to someone I can't understand, and who wants to sell me a new $300 power supply (the only way I can be sure it's compatible according to them) before they will even TRY to troubleshoot my issue.
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More about fails boot
  1. Welcome to the forums, Newcomer. Your post suggests that there could be one or more failures from your current hardware.

    The constant rebooting to get the computer running sounds like there could either be a PSU failure (as unlikely as it seems) or possibly a heatsink fan failure. If the fan isn't spinning properly, the CPU will shut itself off to protect itself from overheating.

    The "other" GPU could also be failing simultaneously, which would, ultimately, suggest a PSU failure, or residual effects from a previously failed PSU. Underpowered hardware can prematurely wear, thus decreasing the life expectancy.

    You mentioned that the electric company replaced meters. Was there any reason to believe that there were power failures/problems? Like recent brown/black outs?

    Before buying any parts to do swap tests; unless you're planning on upgrading, get a digital multimeter and test the P1 connector. The P1 connector is the 20/24 pin socket connector that plugs into the motherboard. Use the multimeter while the P1 is connected, and the power to the computer is on.

    Touch the black lead to any of the black wires on the P1. Use the red lead to touch the following colors. Next to the colors listed below are the optimal voltages. Note that the acceptable variance is +/- 5% except for the -12 volts which is +/- 10%.

    Yellow wires: 12 volts
    Red wires: +5 volts
    Orange wires: +3.3 volts
    Blue wire : -12 volts
    Purple wire: +5 volts standby
    Brown wire: +3.3 volts

    Perform this test inside and outside of the case. By outside, I mean do a breadboard to rule out case shorts.


    1. Remove all connections to the mobo, except for CPU fan.
    2. Remove all hardware from the mobo, except for CPU/Heatsink/Fan
    3. Place mobo on a non-conductive surface (phonebook, wood, cardboard, etc)
    4. Install one DIMM
    5. Reconnect the PSU (remove it from the case, if need be)
    6. Use a flathead screwdriver, or similar tool, to jump the power switch pins (follow the connection from the front panel power button)

    Now that you've breadboarded your system, you are ready to test the PSU again. To further test your system, especially if the PSU checks out ok, turn off your system, and then reinstall the GPU and any power connections to it. Turn on the power using the screwdriver, as mentioned in the breadboarding instructions. If the display to the monitor shows up, wait for Windows to load, and then shut down again. Do this a couple more times for consistency. If the display continues to turn on succesfully with every attempt, you may have a short.

    With your system still breadboarded, attach the front panel connector to the mobo. Now press the power button. If the display comes on, wait for Windows, and then shut down. Repeat this a couple of times for consistency.

    Lastly, jot down any new observations, and then post back here with results.
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