Chapter 14 Managing Devices for FortiOS 5.0 : Vulnerability Scan : Requirements for authenticated scanning and ports scanned : Microsoft Windows hosts - local (non-domain) scanning
  
Microsoft Windows hosts - local (non-domain) scanning
The user account provided for authentication must
be a local account
belong to the Administrators group
The host must also meet the following requirements:
Server service must be enabled. (Windows 2000, 2003, XP)
Remote Registry Service must be enabled.
File Sharing must be enabled.
Public folder sharing must be disabled. (Windows 7)
Simple File Sharing (SFS) must be disabled. (Windows XP)