Thanks for the question. At this time our online backup agent cannot backup files across a network. However, we have helped other customers solve this issue by setting up an automated copy job. Essentially, prior to a scheduled backup, a scheduled task kicks off, copying all of the data needed for backup to a folder that is selected for backup on a local machine. Also, there are no limits to the amount of agents you can install. Installing an agent on the server or workstation hosting the mapped drives may also be an option.
Unfortunately no, the list of supported operating systems for Symantec Online Backup is as follows.
Windows 2000 Server with SP4 URP1 or Windows 2003 Server SP1 or later, Windows XP SP2, and now Windows Vista (Virtual machines in VMWare are acceptable.) 64-bit operating systems are not yet supported.