Exchange 2010: How Do I know If SP1 is installed…

Check the version number on your server, and compare the build number to the numbers below:
Microsoft Exchange Server  2003                     6.5.6944                
    October 2003
Microsoft Exchange Server  2003 SP1                 6.5.7226                
    May 2004
Microsoft Exchange Server  2003 SP2                 6.5.7638                
    October 2005
Microsoft Exchange Server  2003 post-SP2            6.5.7653.33             
    March 2008
Microsoft Exchange Server  2003 post-SP2            6.5.7654.4              
    August 2008  
Microsoft Exchange Server  2007                     8.0.685.24 or 8.0.685.25
    December 2006
Microsoft Exchange Server  2007 SP1                 8.1.0240.006            
    November 2007
Microsoft Exchange Server  2007 SP2                 8.2.0176.002            
    August 2009
Microsoft Exchange Server  2007 SP3                 8.3.0083.006
                  June  2010
Microsoft Exchange Server  2010                     14.00.0639.021
                  October 2009
Microsoft Exchange Server  2010 SP1                 14.01.0218.015
                  August 2010