Any ideas on why a PC when switched on, starts up, shuts down after about 5 seconds and then starts up again. No signal to the screen appears when this happens. I have to try this about 6 times before it starts up successfully with no break and then works fine.

Its a home assembled PC - i7, 6Gg DDR3 RAM

Frank, November 2010

Check for shorts inside the case (a loose screw etc.), then reseat everything. It could be a PSU problem. If not, then you're going to have to take the PC down to minimum spec. and see if it does it then (just PSU, motherboard, CPU + cooler, one RAM DIMM). If not, start adding the components back in one by one until the problem happens again. If it still does this on minimum spec, you will have to try different components to isolate the problem.

Touche, November 2010