Power Supply Issue: Turns on for .5 sec then does not fully turn on.

I recently blew out my power supply. I upgraded from 600w to 750w, I installed it correctly (I think). When I try to power it up, it gets power briefly(some lights turn on cpu fan spins a little then it does not turn on all the way.
I am not sure what is wrong

Thanks in advance

Rosewill RP600V2-S-SL 600W ATX12V v2.01 SLI Ready Power Supply - (This was my old PSU, not sure how bad it was blown out, but its not working)

Current Specs.

LG 22X DVD±R DVD Burner Black IDE Model GH22NP20
Seagate Barracuda 7200.10 ST3250410AS 250GB 7200 RPM SATA 3.0Gb/s 3.5" Internal Hard Drive
AMD Phenom 9600 Agena 2.3GHz Socket AM2+ 95W Quad-Core Processor Model HD960ZWCGDBOX
G.SKILL 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 1000 (PC2 8000) Dual Channel Kit Desktop Memory Model F2-8000CL5D-4GBPQ
GIGABYTE GA-MA78G-DS3HP AM2+/AM2 AMD 780G HDMI ATX AMD Motherboard
XFX PVT98GYDLU GeForce 9800 GT 512MB 256-bit GDDR3 PCI Express 2.0 x16 HDCP Ready SLI Supported Video Card

Current PSU Lifetime Series Pro 750W Psu Model- LSP750

When it "blew out," I was loading a game and at the first cinematic scene my comp turned off.

Thanks for your help!

Yeah that 600 watt rosewill was really a 450 or a 500 looking at its specs.
http://www.newegg.com/Product/Show [...] -%20Retail

Do you have another computer that you could test some of the parts out in? In particular check the ram, and swap the motherboard for another AM2 one for testing. If it boots with a different motherboard then your mobo got fried, only swap out one part at a time though so you can find the issue.

Take that graphics card and try it in another machine if you can, when your PSU died it might have taken the GPU with it and if it caused something in the GPU to short the PSU would shut off to protect itself. If the system you try it in doesnt boot up either you have found your issue, as long as the test system has a good PSU in it it shouldnt pose any risks, but its probably your graphics card at this point. Good excuse to upgrade to one of the newer ones.