For the last few months I know I've had a dodgy (Bestec) PSU on my HP, the light at the back of the PSU flashing, and unable to start the PC until this flashing stopped, which it would after a few mins/hours!
I eventually got a replacement (off eBay) and finally installed it yesterday. The green light is no longer flashing, the PC starts, in that the fans whir away, but then within a couple of seconds, they stop, and green light on the PSU goes off. I tried it several times, re-checking the connections, etc but each time I try its the same.
Any ideas what to check, I re-connect all the power leads as they were originally connected, and the PSU is the exact same make/model as the original...