Have you ever encounter a problem that Windows continuously restart just after the Windows XP logo appear on the monitor screen? And that when you try to re-install from an XP installer, it will appear that its already an unknown partition.
Now your thinking of reformatting your hard drive? Not yet, I suggest to try this action before re-formatting. Try installing the problematic hard drive to a different system and let Windows on another machine repair the corrupted partition, you will be surprise that you can now access all your data.
Once you are able to access the problematic hard drive,back up all the important files and then reformat the hard drive and install new Windows XP.Their are lots of hard drive recovery software available in the net that may also able to fix the mentioned problem, but if you don't have time to look for such utilities, you can try my solution and it might save your precious data from extinction.