If I understand correctly, you formatted drive C: on which you had xp installed
I would think your xp installation is now gone, and that you now want to reinstall xp, and do not want fedora on the computer anymore.
If that is the case, then you can reformat the entire hard drive and use the xp installation CD you have.
It is interesting that you could not format the hard drive and install xp using the xp installation CD you have.
When you begin to boot your computer, use one of the function keys (F8 or F10 or ....) and enter the BIOS settings. Make sure that you have set your BIOS to boot from the CD drive first. Your BIOS settings may incorrectly be set to boot from the hard drive first, in which case it will look in the boot sector and find grub, which normally allows you to select to boot into xp or fedora. You may have broken grub during all of the changes you have made so far, and that is why you are getting a blank screen.
Once you make sure that your BIOS settings attempt to first boot from the CD drive, you should be able to use your xp installation CD to format the hard drive (which will get rid of fedora) and then reinstall xp.
If your BIOS settings are already correct, and your xp installation CD still ends with a blank sceen, you can go to the following web page and download an xp setup boot disk (diskette) and use it to prepare your hard drive for reinstallation of xp, if you have a diskette drive.
Hope this helps.