Help - random reboot hell (didn't really know where to put this)

Hi, I have a PC running Windows XP which I've had since Feb 2004 and which has been beset with problems ever since I got it. I've recently solved a major CPU overheating problem which was causing the processor to overheat every time the computer was turned on, causing it to crash to a blue screen of death. I solved this by cleaning out the CPU's heatsink and replacing the thermal grease between the processor and the heatsink.

Now, however, there seems to be another problem. In fact, it appeared when I was reinstalling Windows after a complete hard drive reformat right after I had finished putting the PC back together after replacing the thermal grease. Basically, the computer is rebooting itself at completely random intervals. There is one thing about these reboots that strikes me - Windows is not reporting any errors (no blue screens even with reboot-on-error turned off, nothing appearing in the system logs, no "report to Microsoft" prompts, no "your system did not shut down correctly" messages... nothing. It's as if somebody is sitting there pressing the reset button at random intervals. The beep and the flashing of the keyboard lights is exactly the same as when you press the reset button. These reboots are happening frequently enough that the computer is essentially unusable.

I have tried the following already, to no avail:
- Unplugging the reset button from the system
- Removing both of my CD/DVD drives and my sound card
- Unplugging all the peripherals except the keyboard and monitor
- Completely de-dusting the inside of the system

Another bizarre observation is that system does not seem to reboot randomly outside of Windows (i.e. before Windows loads up, like in BIOS). It DOES however reboot randomly during the installation of Windows itself, but not during the reformatting of the hard drive (which takes place outside of Windows).

The rebooting doesn't appear to happen in safe mode, but for some reason the CPU fan does start spinning at very high speeds and the CPU starts heating up even though the PC is not apparently doing anything. The rebooting DOES, however, happen in safe mode with networking enabled...

Please note that I really don't have any money to spend on this unless I have VERY good reason to believe that what I spend it on will fix the problem, and I don't have spares of anything lying around to swap out components with. I have already replaced the PSU about two years ago. I have also replaced my RAM within the last two years, and I have run memtest86 and found no problems. The only other internal hardware that has changed since I first got the PC is a DVD-RW drive which I installed after replacing the thermal grease. Note also that I have previously performed another reformat/reinstall without any problems at all.

The problem has suddenly become worse today since I've plugged back in more components and started installing some drivers - the computer now hangs for about a minute before the memory check at startup, and again for about two minutes before the Windows login appears.

That's all I can think of for now, let me know if more information is needed. I apologise if I have posted this in the wrong forum.
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  1. Possible PSU issue. Sounds like fluctuations in power, get a new PSU soon (the rebooting with no blue screen is suspect). Try this first tho: re-setting the CMOS, by powering off, unplugging the power, and removing the CMOS battery for about 10min. Put it back in, plug the power in, and boot.
  2. Possibly a driver issue if you reinstalled Windows XP... Are you sticking to SP1a/SP2 (the most stable versions)? Also watch out if you install Windows XP the original (i.e. SP0) as this has more security holes than a sieve. In fact you can't hook it up to the internet until you have a 3rd party firewall installed and/or updated to >SP1a!! Also have you checked that you have the right/newest drivers for all your hardware?

    I would download ProcessExplorer (a freeware utility now published by good ol' M$ themseleves). If things are running a muck on your system, Windows Task Manager will be like a microscope covered in mud - you need a supercharged replacement!! Check out the top fields of the ProcessExplorer window next time the CPU fan goes wild... Does the Hardware Interrupts go made or is there any OS processes hogging the CPU??

    What make/power rating is your newer PSU?

    How much RAM are you running? HD size/ pagefile size??

    MB and chipset?


  3. Since it's giving you guff when starting, it could be the PSU or Motherboard. Check your motherboard for any leaky capacitors. It could so be your RAM. To check the RAM do the following.

    1) Set your RAM to it's lowest possible speed setting and highest, slowest possible RAM setting, ie longest timing command, biggest CAS delay, etc.

    2) Try running the system with one RAM stick at a time.

    You may find that one of the RAM sticks is giving out or just doesn't want to run at it's advertised timing anymore. If you see any leaky capacitors though you can either get a new motherboard, or be good with a soldering iron.
  4. Did you try to make a clean install of XP? Try it and look whether it still reboots. That way you can make sure that it is not some crappy driver/service which kicks your XP butt.
  5. did you build this computer yourself?

    if you did check to see if you put a standoff in the wrong place and its shorting out the board. also do the shake test - make sure there isnt a screw moving around in your case.

    go into bois and load defaults - after which check all the settings and make sure they look correct - even default settings can be wrong.

    next - are you sure you have the cpu heatsink on properly? - make sure its not the wrong direction - depending on the socket you can actually insert the heatsink the wrong direction and the main portion of the heatsink will be off a bit from the cpu.

    remove as many components as you can - including ram - leave one stick in - if it crashes swap it out with the other one and try again.

    make sure all your connections on the motherboard are inserted and make sure you didnt miss a power plugin on the motherboard or videocard.

    thats a few things you can try.
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