Dead computer!?

[Emphatic]

Yesterday my computer randomly shut itself off.. When I went to power it up again nothing happened. The light on the front of the computer indicates power but the computer itslef wont start up. I did notice that the cpu fan spins for about half a second when you try and power it on but then immediatley stops.

To me it sounds liek it could be a psu or a motherboard problem, but dont know the easiest way to test or find out whats wrong?

Any help would be much appreciated!

 

[Emphatic]

I didnt make it very clear in the first post but the light on the front of the computer stays on even though the computer wont boot up, does this still mean it could be a psu problem?