A UNC path (\machine_nameshare_name) is the recommended method for specifying a network location for the administrative image installation directory. However, you can use a mapped drive as the location for the StartSWInstall.hta file in the administrative image (for example, U:StartSWInstall.hta), provided the installing users all have that same drive letter mapped to the administrative image shared directory.

For example, if you mapped the U: drive to the administrative image shared directory, the notification email will instruct the users to click a link to file://U:StartSWIOnstall.hta. Users receiving the email can successfully install provided that the U: drive is mapped to the UNC location for the administrative image (\machine_nameshare_name).