Your OneCare Circle will only show the PCs that are using OneCare version 2.0, non-beta, and activated with the same LiveID. The printer and wireless router are not part of your "circle" although they are devices on your network.
So, is OneCare installed and activated on the laptop? What version is it running? Have you made the desktop PC be a "hub" in the manage your OneCare circle option?
-steve