Convert from Fat32 to NTFS

I recently upgraded my wife's Win ME computer to XP. Had no problems with
the installation and it has been running flawlessly for a couple of weeks
now (maybe I was just lucky). I would like to convert the file system from
Fat32 to NTFS but don't want to screw it up since it's working so well. How
dangerous is it to do the conversion? Also, she has a lot of files backed up
on CD's and even some 3.5 floppies. The computer is used with a high tech
sewing machine and it would be disasterous if anything was lost or
corrupted. Do the CD's and floppies have to be converted too? Is the
conversion pretty fail safe or should I just leave well-enough alone? Any
advice would be appreciated.
Thanks!