Hi,
I had in mind that the drive is mapped to NTFS folder. If the disk does not have a letter or not mapped into folder, defragmentator of system does not see the partition.
When I asked to correct gadget "Driver Monitor", the author sent me program - wmiexplorer through which he learned how to read the information about that disk.
The figure shows which partitions are mapped (in Windows XP don't work).
In other programs (word, totalcmd) the disk used as folder.
Total Commander change information about disk, when changed partition (drive).