Ok guys - I thought I would do a good thing and take the computer out and blow the dust out of it. I did that and got everything plugged back in and now it won't start. All I get is flicker of power and the PSU fan twitches for about an 1/8 of a second and the MOBO light is always on. I have checked all the connections and they are fine. I have an ASUS P4P800 and I am wondering if that is the problem. It worked fine before I blew out the dust. I guess I should have left it. So what do you think powersupply or MOBO. Many Thanks.