There are several ways to find out the sql server edition/version and service pack levels. Some of the common methods are
3.Open the SQL Server Error Log file and you would find this information there.
4. Go to Run–>type ‘RegEdit’–> HKEY_LOCAL_MACHINE–>SOFTWARE–>MICROSOFT–>MICROSOFT SQL SERVER–>MSSQL10.50.MSSQLSERVER–> SET UP.
Methods 3 and 4 are useful when you cannot connect to sql server but you want to find Version/Edition details of your sql server.
http://www.SQLServerbuilds.blogspot.com is a very handy website when you want to find information on sql server builds, latest hotfixes and patches.