The PSS SQL Server Engineers made a nice blogpost explaining How to Rebuild System Databases in SQL Server 2008
In SQL Server 2005, we introduced a different method than in previous versions to rebuild system databases (affectionately known as “rebuild master”). You were required to use the setup.exe program with command line switches.
This is no different in SQL Server 2008 but the command line switches have changed some and the process behind the scenes to rebuild the system databases (master, model, and msdb) is also a bit different.
The cool part about the way they are doing this is that you don’t need your DVD anymore!
You should bookmark that page immediately so that you can find it when you need and before you suffer that enormous panic attack 🙂

Denis has been working with SQL Server since version 6.5. Although he worked as an ASP/JSP/ColdFusion developer before the dot com bust, he has been working exclusively as a database developer/architect since 2002. In addition to English, Denis is also fluent in Croatian and Dutch, but he can curse in many other languages and dialects (just ask the SQL optimizer) He lives in Princeton, NJ with his wife and three kids.