Compaq Presario won't power up.....

Hey Guys,

A friend gave me his computer to try to fix. It is an older Compaq Presario model. When you plug the power cord it the light on the back of the power supply blinks as does the power button light the computer displays nothing onto a monitor and you cannot force a shut off via holding the power button.

I at first thought it might be the power supply, but tested that at the local computer shop (they hooked it up to a tester and said it was stable and the voltage was fine)

Not sure what else to try next. I tried removing the motherboard battery to reset bios also, but the same problem and it still will not boot up or turn off.

Any ideas?

Thanks

Brad