Easy tiger. In theory, you're correct. In practice, FC2 is notourious for screwing up your boot partition and not letting you boot back into Windows.
LWN: Making Fedora Core 2 and Windows play well together Should help you out with it. You can even prevent the problem.
Otherwise, go for it.. good luck.
Actually, re-reading your post.. defragging won't do anything. You have one hard drive, I take it.. and wnat to have both Windows and Linux on it.
You need to partition the hard drive, so Windows can't see the free space anymore (leave it some!), and Linux has some space to create it's own partition (depending on how much you want to do with your Linux machine, up to 10 gig would probably be good).
There are programs like Partition Magic for Windows or parted/qtparted for Linux that can do this. I highly suggest using Partition Magic. It's easier on beginners and a bit more stable. Don't want to go wiping your Windows drive hehe.
BTW, you'll want to keep Windows as the primary partition, and install linux on the subsequent partitions (it'll probably going to make 3.. one for /boot, one for swap, and one for root (/)).