Cannot start up computer or shut down

[madcaplaughs432]

Last night, I tried to shut down my computer and couldn't. Instead it restarted itself. Impatient, I decided to unplug my computer.
This morning, I plugged my computer in again and it started itself up without me doing anything, but nothing shows up on the screen and it continuously turns itself on and off every second or two. The hard drive spins, the lights blink, and my speakers turn themselves on, and it repeats this process continuously until I unplug it again. I've tried everything I could think of. I checked all the plugs, tried letting it rest for about an hour, and it still keeps doing this.
I'm wondering if maybe I have a virus, but I run virus checks every day and nothing has showed up.

I have Windows XP and I'm not sure of the brand of my computer.

Any suggestions?

 

[raybay]

You have some work ahead of you, as it could be hardware, memory, or an infestation... and tricky to find.
First, tell us the brand and model, or the motherboard, and the age... as well as the OS.
My guess is that you have an infestation.
Does it start up any better in safe mode? If so, go there after downloading AVG Free with a different machine.
Then go back to the most fundamental install... disconnect everything you can do without, and let us know what happens.