Excluding specific operating systems from scanning isn't possible, if this is what you're asking. This is not something that could reliably work, as we can't know what a machine's operating system is without scanning it.
To prevent unwanted machines from being scanned, you need to either ensure that those machines are not submitted for any scanning method under Configuration\Scanning Methods or specifically exclude the machines from scanning. You can exclude asset types, domains, specific Windows computers and specific IP addresses. (In the 6.0 beta, you can exclude IP ranges as well.) More info on exclusions can be found
here. If your machines use naming conventions, you could use wildcards in your Windows exclusions. "LAN%" for instance excludes any Windows computer whose name starts with the word "LAN".