Uhm, if you delete the partition, it's gone. I've installed XP hundreds of times. Not once, EVER has a deleted partition hung around. Certainly if you don't delete it, you can have two installations listed. If you delete the partition it's gone. Period. End of story. No ifs, ands or buts. You also can't create an NTFS partition with Fdisk.
You have to hit the L key to delete a listed partition. If you didn't do that, certainly it'll still be there.
I create no partitions with FDISK.
I just blank the drive.
The CD then creates the NTFS partition when I reboot with it the drive.
I've had the "double installation" happen several times even after "deleting" the partition via the WinXPPro CD..
YMMV.