You already stated you tried FixBoot, FixMbr and BootCFG so I guess you ran them in the Recovery Console which would have been my answer to your latest query.
I strongly recommend that you do not even attempt to install any Operating System until you have scrutinised your partitioning and the condition of your data files unless you are prepared to lose the lot
That was my reason for asking if your backup is up-to-date. If it's not up-to-date you should try to recover critical files before taking a chance on their being over-written.
You didn't respond to the query about your partitions and whether a partitioning tool was used to 'delete' the 'extra partition' (Replies #3 and #6), it's possible that no partitions now exist, not even the partition on which XP was originally installed.
The
Diskpart utility [highlight]might[/highlight] be of some use but I have never used it so cannot comment on its suitability.
Sorry, I'm out of steam on this one, someone else might step in
Good luck