From: DeskNow Knowledge Base
http://www.desknow.com/kb/

How can I backup to a Windows Network drive?
http://www.desknow.com/kb/idx/9/110/article/

You are getting a 'BACKUP FAILED' message with the error 'The system cannot find the path specified' when trying to backup to a Windows Network drive. Why?

When DeskNow runs as a Windows service, by default it is run as the local SYSTEM account (which is the default for most services). This account, however, does not typically have access rights to network drives.

To let DeskNow access network drives when running as a Windows service, go to the Control Panel/Administrative Tools/Service section, right click on the DeskNow service, select 'Properties' and in the 'Log On' tab enter the logon details of a Windows user account that has permission to write to the network drive you want to backup to.

Then restart DeskNow. To backup to the network drive, use the notation \servername\share instead of Z:\backup or similar, as drive mappings often are not set up for a service.

NB to speed up operations when backing up to a network drive, it is highly recommended to configure DeskNow to use a temporary local directory, which should be a folder on a local drive. DeskNow will build the backups on the local drive and then move them to the network drive in a single operation - which is MUCH faster.