If a user browses to a file in my app, and I get back something like "F:\Docs\SpringQtr\The.doc", how can I find whether the F: drive is a hard disk from a machine that has many, a CD, or a mapped drive?

And—more importantly—how can I find what the UNC is for that particular mapped drive?

use the Drive object (from FileSystemObject.GetDrive)

property DriveType tells what sort of drive it is (see the DriveTypeConst in the VB Object Browser)
and ShareName property gives UNC path

rgds
Phil