DNS Aging/Scavenging
http://myitforum.techtarget.com/articles/16/view.asp?id=6287 Dynamic DNS/ DHCP and savaging processes explained on Windows DNS servers.

ISA Server VPN Quarantine - to be researched:
http://fesnouf.online.fr/qss_main.htm Frederic Esnouf (MVP-ISA) website - he has an application that simplifies this. Need to research, but this looks like the way to go, based on some newgroup discussions.

Some sample scripts:
http://www.microsoft.com/downloads/details.aspx?FamilyID=a290f2ee-0b55-491e-bc4c-8161671b2462&displaylang=en
http://www.techgalaxy.net/Training/2824/sample_quarantine_script.htm
http://www.only4gurus.com/v3/download.asp?resource=6893
http://www.windowsecurity.com/articles/Server-2003-Network-Access-Quarantine-Control-Security.html