NTBACKUP and Network Drives

Here’s my situation.

A Win2k Server (Domain Controller) that we
use for performing our backups has over 19 network drives mapped. When I go to ‘My Computer’ I can see all the network drives present. But yet when I open NTBACKUP under ‘My Computer’
not all the Network drives are present. About nine of them are not present.
What is a good way to fix this problem??

Thank you
Nando