System not booting

[Catalyst18]

Problem with parents' system: When power is pressed, the system cycles on-off every 3 seconds, as is evidenced by the optical drive lights repeatedly flashing. With just the processor, ram, and optical drives hooked up, it still does the same thing. I tried switching out the ram. No dice. Even without the video card, it keeps doing the same thing.

This system is an AMD Athlon XP 1800+ system based on a ECS K7S5A, with 256mb of sdr ram, stock heatsink, MSI mx440 video card and a "Deer Computer Co." 300w power supply.

I'm thinking power supply, but it smells fine and has run fine for its entire four-year life. What do you guys think?

 

[boomerang]

Have you given it a visual for bad caps?

 

[Paperlantern]

I would try another PSU before using the one thats in it anymore, typically a computer wont cycle like that unless told to by software, ie windows is configured to restart after system crash or something like that.... maybe shorted reset switch?

 

[Blazer]

Ill second that BAD CAPS motion !

 

[Catalyst18]

Tried the reset switch thing, but I'll go look at the caps...