Connect to the instance of SQL Server, and then run the following query:
An example of the output of this query is as follows:
Microsoft SQL Server 2008 (SP1) - 10.0.2531.0 (X64) Mar 29 2009
10:11:52 Copyright (c) 1988-2008 Microsoft Corporation Express
Edition (64-bit) on Windows NT 6.1 <X64> (Build 7600: )
I hope this helps you.