Run and execute the following query; it doesn’t matter what database and/or table you’re in:
select @@VERSION
If executed successfully, you should get something like below, which shows that SP2 is installed.
Microsoft SQL Server 2005 – 9.00.3042.00 (Intel X86) Feb 9 2007 22:47:07 Copyright (c) 1988-2005 Microsoft Corporation Enterprise Edition on Windows NT 5.2 (Build 3790: Service Pack 2)