Quick point: there's no such thing as an ATI/NVidia card to my knowlege. ATI and NVidia are competitors. That's not so much related but ...
If you can't get to Safe Mode that's pretty severe. If there's another video on board, pull the add on card and see if it boots. When a card dies on a physical level it can often hang the boot. Make sure you power off and pull the power plug before removing any hardware.
If that doesn't help, you are likely in need of a re-install. Keep in mind that the Documents and Settings folder will be deleted and recreated during an install. If you don't have all your data backed up you'll lose it.
The easiest way to back your data up would be to install that HD as a slave in a second PC and copy data over. If you can't do so, you could get into the Recovery Console and rename the whole folder to OldDocs before installing to protect your data. If you don'tknow how to do this, let us know. Someone will post steps if I don't; I'm off to a client's now.