Even though you no longer have to worry about disk partition alignment for SQL Server on Windows Server 2008 (you did on Windows Server 2003 and Earlier; see Disk Partition Alignment Best Practices for SQL Server), there are still important tuning parameters and settings that can result in improved performance for the Windows Server 2008 R2 operating system. You can download the document from here: Performance Tuning Guidelines for Windows Server 2008 R2.