If after a fresh install of CentOS or Fedora or after switching monitors on one of these systems you get a blank screen, then your video configuration is probably not correct.

So here is how to fix it;

1. When the grub splash screen is displayed hit any key.
2. Select the CentOS or Fedora boot choice and press the 'e' key.
3. Select the line that begins with something like 'kernel /vmlinuz' and press the 'e' key again.
4. At the end of the line add a space followed by the number three (3), when done press the 'Enter' key
5. Now press the 'b' key
6. Log on as root and supply root's password when prompted and then type:

system-config-display