Depending on the OS you are using you may find the Windows "rsm" command helpful. For instance:
rsm eject /PF"Volume Label" /Astart
where "Volume Label" is a quoted version of the cartridge volume label displayed by Windows Explorer. This works for me with Windows XP.
As for the novice user, has the user been instructed to try right-clicking on the drive letter in Windows Explorer and selecting the "Eject" option? If no other software is accessing the drive this should allow an eject to complete successfully.