Re: What's wrong with my computer?
Sounds like your power supply is taking a poo or maybe it's not got enough juice to handle your setup.
You say that you have a custom built pc, did you build it?...if not, who?
What are you running(how many fans, harddrives, what kind of graphics card, mobo model...)?
What operating system do you have installed?
What type of sites do you frequent when it shuts off?
What happens when you leave it on without doing anything(no browsing no nothing)?
What happens if after the computer decides to not start if you power cycle* your rig and then try and turn it on again while it's still plugged into the same outlet?
*power cycle - While computer is powered down flip the power switch on your power supply to the off position. Push and hold the power button(front of box) down for 8seconds. Release the button. Flip the switch on the power supply back to the on position. Finally push the power button on the front of the box to power the system back on.