multi booting can me an idea as to how to install and set them up.
Ok first off make sure u have one of your hard drives free, IE have no data on there that you want to keep, maybe transfer all of the files to a folder on your Windows Drive.
Now insert your Ubuntu OR Fedora Core 3 Disc 1 and restart the computer. The computer will boot into Linux and start to install.
It is very simple; you may have trouble with the partitioning though. I usually partition 1gig of space for my swap drive and all of rest as "/" using the file system ext3.
Linux will not touch the Windows drive by default but double check before u click format.
It will set up the boot loader and everything by its self so you should have nothing to worry about.