I'm fairly certain if they don't have the Professional versions of Windows, they won't show up. SBS Standard requires you to have Professional on all computers.

I had to upgrade the BackDesk Computer and FrontDesk Computer to Win 7 Pro for them to show up in the list. It was a time saver for me since I made an image for Pro and I use Group Policy like folder redirection and other things. So I simply upgraded those computers to the Pro versions. (Win 7 Home Premium to Pro Anytime Upgrade and Vista to Win 7 Pro Upgrade). Much more cost effective for both parties.
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