There is a known issue with SQL Server 2005 SP2 that occurs if you have moved the system databases to another location. Specifically, the mymssqlsystemresource database. If the mymssqlsystemresource transaction log has been moved from its default location, the installer for SP2 does not recognize this. The installer places the new mymssqlsystemresource.ldf file in the same directory as the mymssqlsystemresource.mdf file regardless of whether this is where you have moved the .ldf file to. After the SP2 install, SQL Server services will not start. To fix the issue, simply copy the .ldf file from the directory where mymssqlsystemresource.mdf lives and place it in the updated location and restart the SQL Server services.