First thing you may want to do is save any documents, photos, etc., you want from Me...before you take the plunge...
Once that's done...you really don't need to fdisk...
All you need to do is insert the XP CD and boot from it...
Here's a good guide to follow:
http://www.saviourpc.com/windows_xp_clean_installYou can remove the partition that currently holds Me...create another partition...then format (preferably NTFS) the hard disk that you'll install XP on...
The reason I asked about Me...
Me has got to be one of, if not, the worst operating system Microsoft has offered to the general public.
The only thing good that came from Me is that it gave us XP...
Let us know if you need any additional help...