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Computer keeps rebooting

First a rundown on recent failures:
- white screen appeared during working
- white screen appeared after Windows logo on boot
- no signal into monitor at all

- exchanged graphics board
- started again but reboots after a while of work
- tried fresh install of XP
- reboots during install process (still in DOS part of setup)
- tried new HDD, same result

- ran memtest86 which showed errors on test #5 at around 98%
- tried new RAM, worked fine for some hours, then again reboots were happening
- ran memtest86 on the new RAM, again errors on test #5

Is it possible that some other defect, can cause the RAM errors? Like the power supply or something else?

Any help would be greatly appreciated!
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1 Solution
Danny ChildIT ManagerCommented:
The motherboard can be at fault - hard to test without a direct exchange.

Your fresh install shows that it's not software related.

you should also check CPU temps - google for Motherboard Monitor program
more than 70 deg C is a bit scarey - if it's hot, check for good thermal paste and that fans are spinning nicely.

Unstable Power Supply Units can cause reboots too.

Run it on a very minimum spec - remove all spare cards, disconnect optical drives, one stick of RAM only and see how it is.  Try different sticks in different slots to see if that helps.  If you still get either reboots, or MemTest errors, you should replace the PSU first (cheaper), but the Mobo is next in line.

AirTimeAuthor Commented:
Well, I installed MoBo Monitor.
Here are the results:
CPU is at 50°C...not as low as I hoped for, but not near limit.
Rest seems good, except for the -12V voltage which shows as -3,6.

On my other machine, there are variations of up to +-3V but not as much as this.
Could that lead to RAM failure or might the RAM be okay with proper voltage?
Just in case there is a BSOD flashing past when this happens,disable auto restart on system failure.

1. Go to Start -> Control Panel -> System (Windows button+Pause works, too)
2. Go to Advanced
3. Under the Startup and Recovery section, click Settings...
4. Under System Failure un-check "Automatically restart"
5.Click OK and OK again
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AirTimeAuthor Commented:
Nope, no BSOD whatsoever.
I would have to put bets on the power supply, have you checked the capacitors on the motherboard for bulging or leakage?
check if your pc is not underpowered :  http://extreme.outervision.com/psucalculator.jsp        - - or try another PSU
>>  Is it possible that some other defect, can cause the RAM errors  <<  YES : the mobo  can cause it (eg ram controller, or such)
AirTimeAuthor Commented:
nice link!
but that's not the reason, unless the PSU's just short of expiring. Estimated watt need: 260W   current PSU: 350W

No visible problems on the motherboard. Any other way to check the motherboard short of replacing it?

try booting from a bootable live cd, like knoppix; if this works, your hardware is fine - and V V
AirTimeAuthor Commented:
Tried Knoppix.
"x window terminated with errors"

How can I see what errors there were?
it simply means you have bad hardware.
since you tested with thee minimum, and exchanged ram and video card, your only suspects are cpu and mobo.
you can test the cpu on a compatible board, however the mobo's fail far more often, so that would be my guess
check also for bad capacitors : http://www.badcaps.net/
More problems like this are traced to the PSU, and/or the MOBO than ppl realize.
if the mobo is fine you still need to get a GOOD PSU, like fortron group www.fsp-group.com
There is a HUGE difference between quality PSU'S and that generic garbage that proprietary companies
churn out/use.
Get a UPS too! http://en.wikipedia.org/wiki/Uninterruptible_power_supply
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