intermittent boot problem -- powers on but doesn't POST

[bent991]

My mum has an old duron system that's started to intermittently not boot up.

When the power switch is pressed, the fans power up and the lights go on, but there is no display, the usual power-on beep is absent, and I cannot hear the HDD spin up as usual.

If I then unplug the system and wait a min or so, and try again it might work perfectly or it might do the same thing again.

System specs:

MSI MS6340 motherboard (via kt133) /w onboard S3 graphics
Duron 850
512 mb crucial pc 133 (passes memtest)
some WD hard disk
no-name nic and cd burner

I'm starting to suspect a power supply issue, as the machine is just using an old gateway 200w unit. If there is no POST, it seems like there's just no power getting to the mobo or something.

Any suggestions would be very helpful, as I'm trying to get this sorted out before I go back to school.

 

[PWMK2]

Yeah, it sounds like the PSU, alright. Old computer of mine did exactly the same thing.

 

[Tigerbiten]

As its an old system, check MoBo for leaking caps.

Luck..........