Computer will not start

My computer would turn itself off. It would come back on when I replugged the leads to the surgebuster power point thiny.

Now it will not turn on, even at different power points without the surgebuster.

The LEDs do not work. The fan on the power supply does work. The fan on the processor does work. The chassis fan does work. But, nothing else happens. No power to the CD drives, the monitor or anything else. The computer clock was losing time. There is dust in the computer.

The computerhas been connected to the Internet, but had the Freedom firewall running and the anti virus program Inoculate IT free edition.