Would appreciate a fast reply on this one, guys.

I have a PC with a DG35EC mobo, C2Q Q6600 2.4GHZ processor, 4GB DDR2 800MHz RAM, 500GB Seagate HDD, running on 64-bit Windows 7 Ultimate. The PSU is a Prime Source Tech AX-400S with +3.3V - 30.0A, +5V - 28.0A, +12V1 - 14.0A, +12V2 - 16.0A, -12V - 0.5A, +5VSB - 2.5A. I have now brought a XFX HD 4670 1GB DDR3 card (had a 8500GT before which worked great). My PC refuses to recognize the card and boots up straight to Win7 using onboard graphics. After being through many sites and forums, it seems that voltage might be the problem but have also read that PSUs of 350w (with a collective amperage of 18 on two 12v rails) are able to run the card with not much of a problem and I am assuming that my PSU should be more than enough to power the GPU with 30A (12V1 + 12V2), which is just not happening. Any help would be appreciated as I am planning to return the card tomorrow!

Hello,

So you installed the graphics card. Removed the display cable from the onboard connection, attached it to the graphics card connection and the display doesn't come on?

Does the computer show any VGA BIOS information?

Make sure your actually running the card off the correct rails, also check the efficiency rating of the psu and multiply it by the amperage rating (that gives you the real output)

just refer to the radeon website for recommended power supplies. Or just try reconnecting the card and rebooting and download all latest updates..make sure you dont overclock because your powersupply is quite weak