The Official SBS Blog : Repair Microsoft Exchange Server Roles on Windows Small Business Server 2008: http://blogs.technet.com/sbs/archive/2009/05/21/repair-microsoft-exchange-server-roles-on-windows-small-business-server-2008.aspx
Read the complete post at http://msmvps.com/blogs/bradley/archive/2009/05/22/the-official-sbs-blog-repair-microsoft-exchange-server-roles-on-windows-small-business-server-2008.aspx