Newish System Won't Start

[Big Kev]

I've just finished experimenting with my new build and finally decided upon the following set up, until I get an SSD:

Coolermaster HAF 912
i2500k
MSI P67A GD65 (Rev 3)
Corsair 2 x 2GB XMS3
Sapphire HD5850 Extreme
Silver Arrow
1TB Samsung F3
Old WD 320G HDD
Corsair 620w (5 years old)

I have three Apache's for top/side exhaust and everything seemed great, until ten minutes ago, when everything went off and the fans were starting up, then turning off constantly.

I turned it off, pulled the plug and on again, but the same result, fans starting up, going off and on again, but not kicking in, so I can't even get into bios. I've tried clearing CMOS, but no change. The cable is working fine in this old computer.

Is this a sign that my psu has given up, or is there another answer?

 

[RJC]

Try single memory module only.

Is there a possibility of testing the psu in another system.

 

[Big Kev]

I've tried one stick of memory in various slots, no go.

I'll try the psu in my old computer tomorrow night, cheers.

 

[mp260767]

have you got an old gfx card you can try instead of the 5850 ?