A friend's Windows 7 laptop no longer allows access to the 'D:' Drive. The partition is still there, and contains his data. Booting with Knoppix we were able to mount the partition and access all files!
How can I tell Windows 7 to 'mount' the partition as 'D:' (or any other drive name)?
The Windows XP method of using Hard Disk Maintenance doesn't seem to exist any more. (see Mokubai's answer, his description of how to get to 'diskmgmt.msc' is what I meant.
The option to assign/change a drive name or path is 'active' for the 'C:' drive, but only a 'help' label shows for the 'D:' partition. There is also no mention of the name / structure (Data/NTFS) for drive 'D:'.
Do I need to rebuild the partition table?
The second part (why backup/restore didn't 'work') of the problem is described here: How to preserve diacritics when cross-mounting drives to Windows7 and Linux