Unable to start SQL Server Instance 2008 R2 - DB file corrupt
Look here  http://msdn.microsoft.com/en-us/library/dd207003.aspx.  It's for 2012 but 2008 is basically the same.  It describes how to use the setup.exe to rebuild the system databases.  From there you have to do restores for your system databases &amp; patch your instance but it works.  If you don't have backups of your system databases you can copy the files off (not master obviously) and copy them back after the rebuild.  It's not recommended but it will work.