How do i completely uninstall graphics card software?

I will try and put it short - i used to have an ATI card but i "upgraded" to an Nvidia but i still have files and folders to do with ATI, and i have a process called 'atieclxx.exe' which takes up 2k of memory. Is their a way to uninstall this junk cos i dont want it interfering and causing conflict with my Nvidia hard/software. And i just found 1 file which is C:\ATI\Support\9-7_vista64_win7_64_dd_cc… and that contains stuff.