Actually, any distro of linux that allows you to install to empty space on a HD, without disturbing the rest of the drive would work. But Fedora seems to have the most user-friendly installer around.
First, if it makes you feel more secure, go ahead and backup your important files. Stick in your knoppix/gparted disk and reboot.
These instructions work for both QTParted and GParted. In knoppix, Open up a root terminal, and type qtparted. In GParted's LiveCD, GParted should be displayed already. Select your harddisk and right click on the big box that says NTFS. Select "Resize", and cut it in half. Click the save icon in the upper left corner to apply the changes. When you click this, the program resizes the NTFS filesystem (moves fragmented files closer together, etc), and then partitions your disk, giving it an NTFS partition, and a blank one.
Now, reboot your computer, and take out the CD when linux tells you to, leaving it aside. If you are using the GParted cd, right-click the 'desktop' after closing out GParted. Eject the CD then just power-cycle the box. You can dispose of it, or erase the CD if you want now. When windows boots up, it'll say it is checking the integrity of the filesystem, and other useless pap. Let it run through this. When you log into windows, go to My Computer, and look! You now have a C: drive that is 50% smaller!
Make your fedora CDs (I make 2 of each, as I tend to accidentally scratch them often), put Disk 1 into the drive, and reboot. Configure it as you want. Tell it to install everything to the free space. When you get the option, install the bootloader to the Master Boot Record. After all this is done, reboot, and you'll see the GRUB boot loader. Let it go for a bit, and you are now booting Fedora.
After the initial configuration of Fedora, restart your computer. When you get to the GRUB bootloader screen again, push any key, then select Other and hit enter. You are now booting windows.