I have Visual Studio Team System Team Suite 2008 with SP1, latest updates and
Microsoft® Visual Studio Team System 2008 Database Edition GDR R2 (http://www.microsoft.com/downloads/details.aspx?FamilyID=bb3ad767-5f69-4db9-b1c9-8f55759846ed&displaylang=en) installed.
In a database project, when I go t to Data -> Schema Compare -> New Schema Comparison, if I select a database that's part of a web project inside my solution as either Source or Target Schema, I get an errror "Schema Compare does not support the specified database" This doesn't happen if I select a Project as both Source and Target.
It seem the tool doesn't support attached databases on SQL Express. No problems when using a database on a remote DB server.