What it is asking is for the volume label.
If the drive you wish to convert is just a letter, e.g. C, then just press enter.
If you call the drive a name. e.g. ziggs drive or any other name, you must enter that name and then press enter.
You can convert any drive, or partition. You just do it one at a time.
The only difficulty on seeing a ntfs drive, would be if you duel booted with win98. Win98 would be unable to see the contents of the ntfs drive.