For question 1, see this post:
Incorrect Status & False Alarms For question 2, if the new PC is using 64 bit Vista, then OneCare printer sharing will not work with the 32 bit XP. You can share it manually with Windows File and Printer Sharing.
Open OneCare on each of the computers.
Click Change Settings
On the firewall tab, click configure firewall
If the network is shown as Public, click Change Location to change it to "Home or Work."
Click the Advanced Settings button
Click Network connections tab.
If there are multiple active connections shown, you may need to disable the extras in your Windows network connections settings. (Network and Sharing Center, manage connections, in Vista; Right click My Network Places and select Properties on the Start menu in XP)
On the Ports and Protocols tab, add a check mark next to File and Printer Sharing - for subnet and Internet if the first setting alone (after all of the above are verified) does not allow Sharing to work.
If all of the above fail, please contact support.
How to reach support (FAQ) - http://social.microsoft.com/Forums/en-US/onecareinstallandactivate/thread/30400b52-7f26-4ba0-bc18-17e305329d90
Once you've configured File and printer Sharing to be enabled through the firewall, see this article to share the printer:
http://www.microsoft.com/windowsxp/using/networking/expert/honeycutt_july2.mspx
-steve
Microsoft MVP Windows Live / Windows Live OneCare & Live Mesh Forum Moderator
