Essentially, yes, it is possible. It's essentially a remote install of FC.
- Defrag
- Repartition to have a small partition in which you unpack the .iso
- Install grub (That's the tricky one. you'll have to use grub4dos. The PuppyLinux wiki has a good walkthrough, although they do it slightly differently than I suggest)
- Boot from the new partition
- install fedora over the XP partition
- boot into fedora and remove the partition in which you've unpacked the .iso
- resize the fedora partitions appropriately to recover the lost space.
But it remains easier to grab your disk and get a friend to install it for you on a separate machine.
for more info on remote, headless installs have a look at the depenguinator or The Archlinux wiki. You have the advantage of having access to the screen/kbd and so don't need to set up ssh.