[sleuthkit-users] Master boot sector problem

[gints <gin...@me...>]

Hallo, any ideas, why happening this:
HDD - ExcelStore 40Gb
File system - NTFS (primary, bootable)
OS - Windows XP

After attaching HDD to IDE or IDE USB adapter (as secondary disk),
the Master boot sector comes affected,
only these records remains
SO 440 - EF DF EF DF
SO 510 - 55 AA

Is there any other reason excepting viruss?

Thanks,
Gints Erglis.