I have a Dell Dimension 4600 which is about 3 yrs old. P4 2.6 GB processor and 1.5 GB of Ram. MOBO is Intel 845p To start, I know my way around a PC and am comfortable making changes and upgrades on my own. Lately I'll log onto my PC, be logged in for anywhere from 10 to 30 mins and then the PC will just shut down for no apparant reason. Weather I'm on the internet, playing a game, or just checking email. The front LED on the tower will then flash green and not allow me to turn the pc back on. I leave it alone for a few hours or until the next day and I'm able to boot the PC up again but will only get another 10-30 mins out of it once again. I have done all of the following: -Confirmed the fan is running on both the power supply and the video card. -Changed out the power supply....same thing happens -changed out the memory...same thing happens -changed out the motherboard...same thing happens -completely disconnected everything from the motherboard and reseated all of it....again same thing happens. I've spoken to the morons at Dell Support, who have provided no help. I can't imagine that 3 yrs is the life span on a PC these days. Escpecially since I am still running a P3 700 MHZ w/ 256MB of ram with no problem. This PC is for basic use though, internet, email, word docs, etc. I need my main pc up and running. Please help.