No power when switching on computer

[zelda]

Hi,

My computer still quite new, but yesterday when I wanted to work on it, nothing happened when I switched it on, could it be the power supply, or is there any other reason for this happening?

Zelda

[Sylvander]

Use these for guidance...
Sylvander’s Diagnostic Flowcharts
Download a copy of my diagnostic flowcharts from here
www.erniek.eclipse.co.uk/downloads/sylvanderdiags.zip
and print them to leaf through.
Begin on the STARTUP chart.

Does the PC really appear "dead"? [No fans, no LED's blinking?]
Can you test the PSU output voltages, or swap it out for a known good PSU?
Do this and/or...
Strip the hardware back to the bare bones.
Ideally the mobo would be out of the case on a non-conducting surface with only PSU, mobo, CPU+fan connected [no video card or RAM].
The POST should run, test, and because there's no RAM give RAM test failure beeps. That would tell you the POST IS running.
If that happens, begin reconnecting hardware one item at a time [switch off, connect an item, switch on][video card, then RAM, then the others] until a problem reappears and you'll have found the culprit.
Short the on-switch pins on the mobo [that could be faulty] rather than using the switch.