Pc won't boot up


May 26, 2012
Hi guys, turned off my PC over night for the first time since I bought it 2 or 3 years ago. Now it won't boot.
Theres an orange LED on the motherboard, a green one under the mains supply on the back.
When I press power the power light flashes orange once for a fraction of a second, the fan at the back of the case looks like it tries to spin less than a quarter of a turn, the LEDs on my RAM flash too. The fan then tries once or twice more and spins a tiny bit more than the first time.
I've tried unplugging all USB and FireWire devices as well as hard drives, reseating the RAM, putting the original RAM back in (I've upgraded recently), taking all RAM out, reseating PSU connections.
I have no other PC or PSU to test if it's the PSU. The voltage setting on the PSU is correct.

Any help appreciated, I need to edit a wedding video I'm in the middle of asap!

PC is dell studio xps, one of the first i7 ones to come out ages ago.
Although there are a few possible problems which may cause that, I would suspect the power supply has died.
Depending on your location, you may have a computer shop nearby that can help (they should have a test PSU). I would suggest to make an appointment and have it tested by them - if it is the PSU (and you are in a hurry to have your computer up and running) they can replace it for you - or sell you one to minimize any downtime.