Blank screen after boot up

i have a dell dimension 3000 desktop. i bought a hd2400 ati radeon graphics card. everthing worked fine for a while now. i accidentally uninstalled the ati software (catalyst i believe it is) instead of media center. upon reboot, i am able to view windows loading, then it goes blank. i have tried about every possible troublshooting step possible. after i installed the new card, i had to go to device manager to disable the oem card to get the new card to work.

the pc came with an onboard oem graphics card. i had the new card connected with the dvi cable. the original card connects with the standard analog (i believe its vga or rbg). i have tried both cards and cables. i even have an adapter to go from dvi to vga. i have tried to boot in safe mode. i have tried removing the graphics card and just booting with the oem card connected, same result. no matter what i try i cant get windows xp to view on the monitor after it loads. neither card will send the signal. i hear it load up but no visual. hopefully i covered everything. any tips would be appreciated! i reset the bios. that didnt work, i then tried again by removing the battery for 30 seconds. it still loads windows xp, then the screen goes blank. i hear windows xp sign on chime so i know the OS loads, but no video.

i can get to that point with either card. if i put the radeon card back in, i can view windows loading, or if i plug in the oem cable and try that way. any other ideas guys? thanks!