[link|http://www.techbargains.com/hottips/hottip13/index.cfm|TechBargains] has a good hyperlinked list of things to do to secure XP. Microsoft has some articles on doing a "lockdown" of user accounts, but it doesn't seem to have anything comparable for limiting internet access (other than XP's limited firewall, of course).

HTH.

Cheers,
Scott.