Best graphic card that is compatible with the Intel® Socket 775

Socket 775 is very old. Modern PCIe video cards will work in that motherboard but a dual core CPU is going to restrict (bottleneck) the GPU. Even an older quad core is too slow for the newest video cards.
 
e5200 2.50 GHz Pentium DualCore processor.
23 inch, 1980x1080.
Windows XP SP3.
MicroVolts aka ToyWars (my brother's playing it)
Battlefield 2 since 3 doesn't really work ...
Call of Duty 4 (would play never versions if possible)
 
Hi

socket 775 is not really relevant as presumably the motherboard supports at least one PCI Express 16 lane slot

what power supply do you have and how many 6/8 pci-e 12V connectors ?

what processor do you have in mind
(core 2 technology varies from 2 core or 4 cores) and speeds up to about 3GHZ without overclocking
[ Pentium 4 & Pentium D's have higher clock speed but are less efficient and give off more heat and are hard to find]

There is no point in fitting the latest fastest AMD/ATI Radeon or N Vidia G-Force card in old technology system

You mention Pentium D which is very old (2006/2007) technology (only available second hand) and slower than core 2 technology.

More importantly what do you want to do with this graphics card and what is your screen native resolution?

give a few answers to my questions and some one will recommended a suitable graphics card from AMD/ATI and NVidia

regards

Mile Barnes
 
I have no idea as to what power suply and how many 6/8 pci-e 12V connectors I have neither do I know how to check.

Yes I'd like to play on 1980x1080, mostly games, internet browsing, movies and maybe some minor editing.