Remote Disk

I have Windows 98 SE client that is unable to map a new network drive. The client has 6 drives already mapped they are F, J, L, M, P, and Q. I can not map an E drive I receive the following error message when attempting to map the drive: “The following error occurred while trying to connect \\server\share Local drive is already in use.” If I go into My Computer it is showing all unallocated drive letters allocated as remote disks. How do I remove this setting of all unallocated drive letters as remote disks?