Here's my build:
Antec 900 case
2x 2gb RAM
700w Power Supply
Quad-Core 2.4 GHz Processcor (Though BIOS is saying it's running at 1.66 right now):
Can't remember what my vid card is off the top of my head, but it's a Sapphire Radeon, and an old model which worked perfectly with my old build. It's the only thing I haven't replaced.
The problem is that my computer will start up, most of the time it will even POST. It's managed (once) to get all the way to formating the hard drive to install my operating system (Brand new hard drive, so it's got nothing on it) but it dies. Sometimes it'll turn on for a second and die. Everything seems to be connected properly, everything seems to be turning on. All fans are running. It seemingly random when it decides to stay on and when it doesn't. I'm at a loss as to what the problem could be at this point =/ I even replaced a brand new 500w PSU thinking that was the problem. I installed the 700w and it still gave me the same problems.