The onboard video may have been disabled but the drivers for it are still being loaded. You can right click on the MyComputer icon to go to the device manager and look under display adapters. If you see two device listings, one for tne new card and one for the onboard, right click on the onboard there to choose the uninstall option. That should see the drivers removed. The other possible problem would be a defect on the new card itself.
has to be something conflicting I have removed the graghics card and reinstalled onboard and it works great once i change back "lock up".If your board has developed a bios fault like what was seen here recently when Windows would freeze(bbrrrrrr....) right up when reaching the desktop a lowering of the memory timings or clock speed would tell right there if the system suddenly ran normal but at the slower speed. Before assuming a hardware defect at this point you could try reseating the new card in the slot to insure it wasn't lifted even a small amount. That would cause problems right there. Besides a video card you want to run Memtest or another memory tester to see if there are any problems found. Systems lockups can have several different sources. A bad install of software? like video drivers?
Once you pull the card out you suddenly see everything normal again? When it locked was that strictly seen on Windows loading or at various points like running a game or browsing some sites online? If it is always right then when Windows loads that would seem to point right at the card itself.