I have configured my scans to use write the FS Asset ID in to the Windows host to allow each scan to identify the same host across the scans, yet each month I see the same machines being reported as new hosts.
Am I missing something obvious (the credentials all seem to work and give full administrator and remote registry access)?
Take a look at your 'Manage Asset Identification Rules' found on the manage assets page at the bottom. Verify the logic for the AND/OR statements and check to make sure that you haven't added anything that might not match in your environment. A common mis-configuration is adding IP address as criteria in a DHCP environment.