Trying to install video card radeon 7000 64mb to compaq presario

Okay guys I am way stumped!! Ive been trying for 3 hrs now to get this new video card to work and it just wont.. Its a PCI video card Radeon 7000 64mb. I went in and turned off the on-board graphics card and installed the new video card and now it wont work! I dont know what to do, please help guys!! thank you!!