The symptom: (You have a NVIDIA card, it was working and this is all you see now)
The above is assuming a few things. The standard Fedora setup includes experimental 3d drivers, and 2d drivers for NVIDIA. So if you've never installed the NVIDIA drivers and you get this prompt, you may have another problem. Check the /var/log/Xorg.0.log file for clues. (or login type "more /var/log/Xorg.0.log")
Installing the drivers:
1. Login as yourself (or root if you have that password).
2. If your logging in as yourself you then need to do "sudo -i". To go to the root user.
3. Type "init 3" This just makes sure your graphics server is shutdown. The installer will complain if it isn't.
4. Type in "ls NV*" to get the file name. This will depend on what driver you've downloaded and is for your card (check NVIDIA Driver Download Page for more info)
Then type "./<filename of installer>". The "./" just means run the program from that directory.
If there is no file then you need to download it. Try copying to a CD, usb key, or you can try downloading via "links ftp://download.nvidia.com/XFree86/Linux-x86/" or "links ftp://download.nvidia.com/XFree86/Linux-x86_64/".
5. Now your at the licence page. Accept to proceed.
6. Answer "Yes" to any configuration questions. (When in doubt, answer yes or pick the default)
7. Your done. Now either type "init 5" to start-up graphics login, or just reboot by typing "reboot".
Typing init 5 will allow you to start using your system without the need to reboot. But for those users used to windows, a reboot at this point doesn't hurt.