Have you tried another psu.I had the same fault on my machine a while back.I checked all the connections on the mobo,still no joy.Then fit a new psu and no problem since. The transformer in a psu stores the current every time you shutdown,so that when you cold boot it doesn't put such an immediate strain on it.If the transformer is faulty it won't hold the charge. One thing you can do before laying out for a new psu is,open it up and give the cooling fans a good clean.A lot of people clean the inside of their pc case,but seem to overlook the psu.Hope that helps Boogs. Here's a link for possible other solutions; http://www.geek.com/discus/messages/23/5227.html?1011321628