Im running Cerberus FTP Server as a service and it can access mapped network drives. Why?
Mapped drives are stored on a per-user basis. The default configuration for a service logs it in as the LocalSystem account, so it cannot access the mapped drives you make when you log in using your own account. You can manually change your service’s account by viewing its properties in the Services Control Panel applet (NT 4) or the Services branch in Computer Management (Windows 2000/XP, Start->Programs->Administrative Tools->Computer Management). A service can map its own drives, or if you are going to use mapped network drives, you can specify the UNC name for the directory.