I have install catalyst for ATI in fedora 17, I'm stuck on a black screen when the system is booting, how can i force the system to boot in command line so that i can remove the catalyst packages??
When the system boots, it should offer to edit the kernel line. Add "single" as a separate word at the end. That way you boot the system into single user mode, a maintenance mode in which only root can use it. Then you can remove the packages.
In any case, I doubt the "just black screen" is due to any packages you have installed, it could be a lot of different things.