How to upgrade my MacPro graphic???

yes but why aren't you using 10.6.8?

100s or more people made that upgrade.

Minimum OS is 10.6.5 so having a clone or something as there was no retail 10.6.7 and it was 2010 that OEM 10.6.4-1/2 came with the Mid-2010 model 5,1

Getting that 2600XT out is over due. There was a warranty on half of those cards.

RAM, disk drives and video cards are normal part of life of machine.

Apple. You can shop Amazon, B&H but you want EFI ROM.

And there are flashed Nvidia cards from MacVidCards on ebay great support and hangs out on MacRumors: Mac Pro section if you want CUDA CS6 and other features and running 10.8.2.

Get the Apple card. Non mac cards are not reliable since they do not use Apple approved firmware.

you seem to know for sure MacVidCards is selling faulty card firmware huh?

If they are flashed PC cards, yes.