There is no one simple answer, but suffice to say you should definitely back up all existing data - and really consider going pure Linux on your machine.
Because honestly - do you need windows? (yeah yeah, for your games)
Important thing before you continue: BACK UP ANY DATA YOU HAVE - LOSS OF DATA IS YOUR OWN FAULT IF YOU SKIP THIS STEP.
Linux and Windows will coexist just fine, as long as your windows partition isn't NTFS (windows 2k / XP) - if it is, then you could run into problems quickly.
If it is Fat32, you can use the tool 'fips.exe' that comes in the Redhat distribution - it also comes with documentation.
This utility will allow you to take the free space from your current single partition and turn that into another partition for your Linux install.
Once you have a partition ready, you need to install Linux following the documentation on the Redhat website.
Redhat has some really great docs, unfortunately lots of people don't read them because they are lazy.
If you don't like reading documentation, or don't like troubleshooting lots of problems for hours on end, you may want to ask yourself if you should really be joining the Linux community!
During the install you choose the method you want to install by, and you partition the drive in one of two ways:
1 - If you have no other OS on this system you can choose "auto-partition" and *presto* you are all set.
2 - If you have windows on this drive you need to choose fdisk or disk druid (disk druid is easier) and you need to set up and format the unpartitioned and unformatted portion of your drive.
Do not format or re-partition your windows drive! THIS IS IMPORTANT.
After this step you have to set up numerous things, and pick what packages you want installed.
If you have tons of drive space, you could always just do a full install - it takes up close to 3 gigs.
For choice of boot loader, choose 'grub' - it can deal with larger drives than LILO, and looks prettier - like thats a good excuse...