Lady F
I assume that you know about a feature of the Ubuntu Live CD: 'parted'
You can re-partition any 'unmounted' file system, leaving the data intact.
(The only time I lost a file system, was the time I saw a small 'Unknown" at the end and decided to reclaim the space
I forgot that that disks partition had been marked "Dynamic" (failed Mirror experiment. XP pro only spans drives
) ,that was part of the Dynamic piece.
)
I highly recommend that you have a UPS with a goodly long run-time when doing invasive procedures like this, just in case