I've had this issue for sometime. On this emachine we have 2.6ghz Intel Celeron, 80GB, it seems when it is cold in the house, trying to start the computer is a beech.... it will sometimes immediatley turn off before posting, over and over.... as you keep doing it, it will get farther and farther. Once it gets to being able to post after several tries, it will keep shutting off...until you unhook the DSL cable. Let it load and after a few minutes you can reconnect the cable. (Doing it immediatly will cause it to shut off immediatly) It has not done this in awhile as it has been warm in the house when turning it on. Only during winter or cold spells. It boots up all the way with no shutoffs. It runs several days at a time with no shutoffs. I boiled it down to either the motherboard, or power supply. My other computer that is offline is built in 2001, and it won't turn on at all when cold until several tries. (cold in house not cold as in cold boot...since in warmer temps it starts up fine.
Anyone ever have this issue? and what does the network cable have to do with it?
(Note that when first starting it when cold in house, unhooking the Cable has no effect...it still does it.)
Any possible solutions would be helpfull.

Cable ? Probabaly not a thing, but it could be due to the PSU...

I figured it was either Power Supply or MotherBoard.... just weird it runs fine in warmer temps. I was thinking maybe there was a broken microtrace in either MB or PS since temperature could affect it.... such a tiny microtrace could possibly not be touching when cold but touches when warm or hot??? This is an issue and I need to know. I have been using roomates machine and now it fails to work properly when cold in the house. (Until it warms up then its fine til late at night when heaters go off; then it just shuts off.) I need to buy either MB or PS to fix it cause he blames it on me using it so much. (Shrug) The last two months it turns on and starts up completely with no fail (it's been rather warm now in house)
Very weird indeed. Any other suggestions anyone?

What Brand of PSU is it ?
A well-known manufacturer or "came with the case special" ?

Hi Have you tried removing all cards and RAM and reseating them it could be a contact issue to.

Yeah -- you can clean those (contacts -- gently) with a pencil eraser
blow out the slots with some canned air.