I have a Dell Dimension 8200. The other day I had two home power outages. The next day my computer powered down after I had left it on overnight. The only way to get it to turn back on was to unplug it....then plug it back in...then it would turn on for an indefinite period of time. When it automatically powers off, there is a blinking amber light on the power button. The numlock button also remains lit...don't know if that means anything.
The computer will stay on sometimes for as long as 8 hours or so...but other times it may only stay on for 15 minutes to 1/2 hour. Usually the longer it is off...the longer it will stay on. I have replaced the hard drive...so that is not the problem.
Also, the power supply fan...and cpu fan are working.
Any suggestions? Thanks for any help.