1) Configure the workgroup computer to enable remote administration.
This script can configure the necessary registry and windows firewall settings: download script
You need to run this script on the remote computer.
2) The scanning account must be an administrator on the scanned computers.
You need a common username/password combination on all workgroup computers, in this example we use the user "administrator".
3) Configure any third party firewalls you might have to enable Windows remote administration.
4) Configure workgroup scanning for your workgroup.
5) Workgroup computers must be visible in the network browser.