The best way is to use the Fedora 9 install DVD as opposed to using the LiveCD. You could get Fedora 10 (testing) as it is due to be released by the end of this month and a release candidate is available.
I'm assuming that you're using an old system as a NAS box. You'd want to select Install or Upgrade in text mode on the initial boot prompt. Answer the regular questions, until you get to the partitioning screen.
Select custom partitioning and the try the following setup
Root filesystem 5 GB mounted on / (ext3) <<< For safety reasons, ideally after removing all cruft it should be around a Gig of used space
boot partition 300 MB mounted on /boot (ext2) << Optional
Separate home partition if you require or else leave it if you don't intend to do any Linuxy stuff apart from downloading.
Whatever space you have left (or disks you have left) can be formatted to vfat and mounted to easy to remember locations e.g /Downloads, /ISO etc.
Now you answer the other questions and move on to the package selection screen. Uncheck the additional softwares (Office and productivity, web server etc). and select Customize Now. When you reach the customization screen, uncheck everything from the desktop environments screen and select whatever servers you require (FTP, Samba). Be sure to have installed SSH. Don't worry too much about installing extra crap, we can get rid of it later.
Now your box is pretty much headless, you can hook it up to your network and do everything via an SSH client like putty. To make things easier set up passwordless logon between your machine and the Fedora box.
You can follow the guide here
blindhog.net Linux - SSH passwordless login with putty
SSH into your box and login as root (remember sudo may not work initially like Ubuntu, you might need to install it). Inside root's home you will find a file called install.log or something (don't remember exactly as I am at work right now). This contains a list of all the stuff you've installed. Post the contents somewhere (pastebin or something) and we can help in getting rid of more cruft to make your box a lean mean machine.
Also you'll need to set up Samba to share your downloads directory so that it is accessible by other PCs on the network (It is quite easy you can find a gazillion guides to do this). You'll also need to install a text based torrent client (e.g. rtorrent). More info on that as we move along.
All the best, sorry if the info was not 100% accurate, currently have access only to a Windows box.
I'm currently using Debian Lenny as a NAS OS (torrent rig, filesharing). Last I checked it weighed in about 800MB with samba installed. Very old system, donated to me by Arya (Intel Celeron 400Mhz/192MB RAM/440LX/Weird MoBo etc). I like debian because server installs are easy and the package repository is huge (like Ubuntu). Fedora is a good choice too, but it is primarily designed to be a Desktop OS (again like Ubuntu) so some customization will be required.
