How can I tell which Graphics Cards can work in my computer?

[hacker1]

I want to upgrade my graphics card, so I was just curious if there was a way to tell which video cards at the store can fit into my computer by looking at the motherboard or anywhere else on the computer?

 

[wintermint]

Find the dimension of your pc case, take a look inside too.. go check what power supply you have... i would get a good quality power supply from Seasonic, antec, and corsair. 400W should run you 6770,gtx 460,6850, and 6870 just fine.