You will need a second subscription for the 4th and 5th PC. The second subscription will need to be created with a different LiveID (email address) as a LiveID can only have one active subscription associated with it.
That means that the 4th a 5th computers will *not* be part of the original Circle.
However, you can still share a printer, just not using the Printer Sharing feature of OneCare. As long as they are on the same network and the network connection on all of the computers is configured as "Home or Work," file and printer sharing is enabled. If the network is wired and wireless, you may need to go to the Ports and protocols tab of the Advanced firewall setting and place a check mark next to File and Printer Sharing for Internet and local subnet.
On the computer that the printer is attached to, right click the printer properties (Control Panel/Printers) and select Sharing to manually share the printer. Then, on the other PCs not part of your circle, go to Control Panel/Printers and add a network printer. The shared printer should appear as available for you to select and configure.
-steve
