Try going to Start -> Run and running "dxdiag" (you can click Yes/OK to the question about WHQL drivers if it comes up)

Check the 'DirectX Files' tab and see if it lists any errors at the bottom of the window.

Also check the 'Display' tab and make sure that your new video card is listed there and is functioning properly.

If all looks to be ok, then try reinstalling DirectX as Yrkoon mentioned and also see about reinstalling EQ if nothing else works.