computer shutting down unexpectedly

I was wondering if anyone could help me... my computer has started shutting down whenever i try to turn it on. It has now gotten to the point that it wont even get to the login screen,so i have no way of seeing what has happened. The computer has been running fine prior to this. I had been running an anti-virus, thinking that maybe something got to it, but now I'm not so sure. I can't even use my computer, I have to use an old one.

Any ideas?

 

If it's shutting down that soon, it's a hardware problem. First thing to check is the power supply; make sure all the power cables are connected firmly (data cables too). Second would be to check your CPU fan and heat sink. Make sure they're clean and the fan is spinning. Make sure the heat sink makes good contact with the CPU and that it isn't loose. You may want to unclip it and add a new layer of thermal snot. Check all your cards and RAM sticks; make sure they're seated firmly. Clean the inside of the case with canned air or an air compressor. Get all the dust and debris out of there. Be sure the power cord is unplugged from the PC before opening the case. Then hold in the power button for 10 seconds or so to discharge everything. If you have access to a 2nd power supply, or can borrow one, hook it up and see if that works.