I'm moving your post to the MultiPC topic folder.
CHanging the name of the PC should not affect the ability of making it a hub in the OneCare Circle. Once you have made a hub n the Circle, you'll want to remove the old entry for the old named PC, since you reinstalled OneCare with a different PC name. It doesn't need to recognize itself - it does need to be activated with the subscription LiveID, though. If you need help with this,
How to reach support (FAQ) - http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=2421771&SiteID=2
-steve