Boot problem PC

Fionn

i was asked to take a look at a PC (Dell Dimension 5000 about 2 years old) the other day. But i've drawn a blank as to whats wrong with it.

the symptoms were it would boot up and load windows then after about 2 mins it would re-boot and go into a re-boot cycle just after the POST

what i did to attempt to resolve this (in order of priority)
tried booting with a Linux CD
i swapped out the PSU and tried one from another PC
looked at the BIOS screen but theres no temp moniters so i don't know if any component is failing due to overheating
checked the fans all would activate on boot-up
took off the processor - reseated put new thermal compound on
took out the RAM mods tried them in the different slots
disconected all drives even the HD and it still went into a re-boot cycle
examined the capicitors to see if they were damaged leaking etc.
examined the board to see if there was anything that would indicate damage nothing apparent
took out the BIOS batt
i didn't check the graphics card it seemed to be working ok
i suspect that some component is overheating because after first attempt at boot the computer will be stable for about 2/3 minutes but after that it will continuously attempt to re-boot. If left for a hour or more it will exhibit the first behavour of being stable for 2/3 mins. Theres no burning smell or any other indication of overheating unfortunately.

am i missing anything???

any thoughts!!

Redisle

Any system speaker/beep codes??
Maybe a short-circuit somewhere? Make sure there is nothing touching the mobo that shouldnt be, something lodged under the board maybe?

Do you have any other graphics card you could try? My graphics card went bust recently and it was doing some funny things to my machine when it happened (reboots,freezing on bios splash screen, kind of different each time).. Even though it may load to a certain point I still wouldnt rule out a faulty graphics card

took out the RAM mods tried them in the different slots

Did you try booting one stick at a time? Its probably not the memory but worth a shot anyway

It could also be the chipset overheating.. I installed a new fan on mine a few months ago and it fell off without me noticing.. My machine was rebooting itself and I had no idea why.. until I found that the fan had come loose the the chipset was overheating..

ab,

Fionn

thanks for the headsup regarding the RAM unfortunately that wasn't it, BIOS beep s are normal and the board is clear of anything that might short-circuit so apart from the graphics card that i'll test this morning i guess i've bad news for the owner

oh well - the joys of computing

Kimbot

Also a corrupt/virused file could cause this. Happened me a few years ago. I could get into Safe mode about 1 in 6 times and when I got in I found the sucker!!

Croc

All Dells have 4 leds on the back, if they are not all green then you have a harware problem. Dells site will tell you what exactly is the prob if some of the sequence is orange.