New rig has lights and fans at first power up but that's it

Hey all, my first post here. I just built a new gaming system and threw power to it and it's not booting. Fans work, lights on the front panel, network cable in back has lights, monitor power led goes green but no boot into BIOS.

System specs:

Rosewill R5604-TBK case
Powmax 400W PS(used from my previous system)
Gigabyte GA-965P-DS3 Mobo
Intel E6600 Core 2 Duo
Zalman CNPS9700 NT CPU Cooler
EVGA GeForce 8800 GTS
Apida 2GB DDR2
Seagate Baracuda SATA 160GB

I've got both PS plugs on the mobo--although the main cable has 4 less connection points on the connector than the board--which following the mobo book was no problem to hook up. The CPU power connector is hooked up. The hard drive is NOT spinning up when I power on, though it should have power and I have the SATA running to the sata0 slot on the mobo. Other than the PS possibly being a little underpowered, I can't think of what could be causing this. Any ideas?

Just looking at the GPU youre using and the PSU......... You want want to try a bigger PSU. The 8XXX series are pretty power hungry.

PSU calculator gives 275W at max load. That is a bit close for a 400W $30 PSU. You've spent a lot of money on that system, buy a PSU with a bit of quality, Seasonic for example. Cheap PSU can go 'BANG' and take out your components!

Mike.

Thanks everyone, the system is working fine now. Turned out that the SATA hard drive wasn't spinning up which was stalling the boot. That's the explanation I got from my local expert who ended up taking a look at it. Replaced hard drive, good to go. I will replace that PSU though, thanks for the advice on that. I was kicking myself for not recognizing my PSU being a vulnerable component in my build. Once again thanks for the replies everyone.