graphic driver

Ok i am new to game dev and i saw Unity and i was blown away. I just downloaded Unity and i wanted to know if Unity is compatible DirectX or Open GL. Im using windows and running Visual Studio 2010 and i have a Raidon 4550 gc 512mb of memory(not the best i know but it works)I just want to know witch one to get or could i run both?

If you can open and run Unity on the card you have, go with that.

Unity is both OpenGL and Direct3D. (Also OpenGL ES on mobiles.)