I've never installed windows after linux, so, take my advice with a grain of salt. you've been warned!
In order to do this, I think you'll have to reinstall grub (the fedora boot-loader) after you install windows, because the windows bootloader doesn't like to share, and will take over the MBR.
also, you'll probably want to partition your hard drive in advance, and make a NTFS partition for windows to live on (I'd recommend gparted) if you haven't done so already.
this from the fedora forums might be useful, also:
It's a tad outdated but it should still help, and it shows you how to fix grub after you get windows running
I have to say, though, that it might be easier to backup your /home and just reinstall fedora after you get windows running.
hope this helps!