I am slightly confuised. RIght now I am a Fedora Core 4 user, and was looking for a linux controller. Type in LinuxCNC and EMC is what I find.
So, when you download the 643MB file, is this like another distribution of Linux? Except, devoted entirely for CNC control?
Or is it like a giant rpm?

sounds like you've downloaded the "BDI". Brain Dead Install cd was created 'cause setting up linux with the real-time kernel extensions can be a real PITA.

If the file has a .iso extension then that's what you got.

Unfortunately, at the moment unless you have someone near by who can show you how it works (or knows their way around Linux) you will have to work on the suck-it-and-see principle.

As far as I know the real time addons that exist is not compatible with Fedora. The RT-add's are a couple of kernel versions after.
Go for the BDI if you don't know too much Linux. But you should also consider the EMC2 as it is pretty stable now. It's a new version and the development team says it's not rock solid yet.

Cheers,
Sven

Building a stable real time system is a little tricky. Your best bet is to go with the BDI. I have run realtime with fedora, you have to get a vanilla kernel and patch it. The RTAI patches are easiest.