I needed to do this to test Crashplan. I keep my photos archived on an external drive hooked to, and shared off of, my router. Since Crashplan’s client runs as a service under the Service account, this was the solution to get it to see these shares.
psexec from the sysinternals suite is required.
Open a command prompt as administrator.
Path to psexec’s location and enter psexec -s cmd.exe.
Mount the drive via its UNC: net use DRIVELETTER: \\server\\folder /persistent:yes
The share will probably show as disconnected. Click it – it isn’t. It should also show up for all users of the machine it’s mapped on.
(Killing the share requires the same steps, only with net use DRIVELETTER: /delete