Booting Problem with graphics card

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ASUS M5A78L-M LX - http://www.asus.com/Motherboards/AMD_AM3Plus/M5A78LM_LX...

There's no 'compatibility' reason for the HD 5750 not to work and the MOBO to post. The typical HD 5750 has one 6-pin PCIe power connection that must be used and connected to the PSU to work. Therefore, make certain the GPU has it's 6-pin connected, and it's properly seated in the MOBO's PCIe slot (top-long dark blue slot) and the MOBO's PCIe lock is engaged.

If it fails then I would try the GPU installed in another PC to see it works. My feeling if properly connected (6-pin) and seated (PCIe slot) is that the HD 5750 is damaged -- RMA is under warranty.

Yes, that is pretty much what i thought. Im gonna try to test the gpu on a friends computer. Ill also try the bios settings.... Maybe its confugred not to start with other gpus then the onboard one. I hope i can make it work, cause it is practcly the price of my whole pc (cpu, mobo, ram, cd, tower together), i dont want to have to buy another one ... Thank god i already had a hd.
Anyways, thanks for the reply. Ill post here if i find a solution.

I looked at the manual when I first replied, by Default the GPU is initialized first. If it's the GPU then most are covered with a 3 year warranty and some longer...if it fails then RMA.