UPDATE (12/17/2007): My blog has moved. This post is now located at:
http://jason.whitehorn.ws/2007/10/31/Enable+MS+DTC+On+Windows+Vista.aspx
To enable MS DTC on Windows Vista simply follow the instructions from:
http://technet2.microsoft.com/windowsserver2008/en/library/1f6d0a27-533b-4516-8656-b492f1649e9f1033.mspx?mfr=true
MS DTC appears to be required to use System.Transactions against SQL Server, and is disabled by default.