I could be wrong, but don't you think the HDD may be screamig 'STOP!!!' I can't think of a single justification, if you don't mind me saying, for a second installation of the same O/S on a separate partition?
OR.. Have you EVER, formatted an NTFS partition on this drive? If you have, you will find it's the "I'm staying-put" 2mb of partiction info, of NTFS.
Incidentally (Curiosity really).. Why... a second O/S of the same type??