Computer won't turn on

[Eck]

I'm by no means an expert, but I do have a hunch as to why my Uncle's computer isn't turning in...

It's a 3 year old Dell, and here's what happens

When it's connected, the green light on the powersupply is SOMETIMES on SOMETIMES off, -- When it's on, I try to press the power button and a small orange light flicker happens, then silence, and the computer doesn't turn on...

It seems pretty straight forward as a powersupply issue, but could it be anything else? (silly question I know)

Thank you!

[Djinni]

Could be a power short on the motherboard due to dust buildup.