Computer won't POST with some video cards, even with a new PSU

I am building pc for a friend from some spare parts, but the computer won't POST or boot up with any video card except for the onboard or an old MSI Geforce 7300 LE. The specs are as follows:

Motherboard: Acer H57H-AM2
CPU: Intel Core i3 560 3.33 GHz
PSU: PC Power and Cooling Silencer MkIII 500W
Video card: MSI Geforce 7300 LE
Memory: 2x 1gb DDR3 (Some lower grade kingston)

The above build is the only one I can get to boot and get to the windows desktop, or without the GPU and using the onboard graphics.

When I try switching to a Radeon HD 5450 or MSI Radeon HD 7770 OC Edition, the computer does not POST or boot. All fans and drives inside are spinning but the system won't turn on. I have tried installing the appropriate drivers before hand, clearing the cmos and still no luck. I have ensured to plug the DVI cable into the video card and everything is seated properly and all power connectors are plugged to the mobo, CPU and video card. I have tried everything in the check list for non posting computers, and I mean EVERYTHING:

I have even replaced the PSU with a CoolerMaster Extreme 2 525, and still the exact same problems with both the 5450 and 7770. The minimum power required are 400W and 450W respectively so these PSU's should be sufficient. The only other hardware that I am running is a 7200RPM HDD and a dvd drive.

I have spent days reading solutions to computers that don't POST and I am still unsuccessful. The only idea I have left is trying a dual PSU setup. Any ideas on what the problem could be?
6 answers Last reply Best Answer
More about computer post video cards psu
  1. Is this a new install of windows?

    What version ?
  2. you say that you've updated all your drivers including your bios?
  3. New install of windows 7 64 bit
  4. And a detail I forgot to give, about a year an a half ago, the PC power and cooling psu was running with the same mobo, ram and the 7770
  5. Best answer
    Try heading for BIOS and finding the setting that will disable the IGP

    Then remove the nVidia driver and all nVidia software and turn the pc OFF when it asks for a reboot

    Then swap in the Radeon

    and try and restart
  6. The bios won't let me turn off the IGP, there is no nvidia drivers, I formatted the drive and never installed any nvidia drivers
    I just tried breadboarding again to make sure and still nothing. Tried some entirely new memory that I bought today for another build, Corsair vengeance 1600 MHz.
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