How to determine which version of SQL Server 2005 is running
To determine which version of Microsoft SQL Server 2005 is running, connect to SQL Server 2005 by using SQL Server Management Studio, and then run the following Transact-SQL statement.
The following table lists the Sqlservr.exe version number.
Release Sqlservr.exe
RTM 2005.90.1399
SQL Server 2005 Service Pack 1 2005.90.2047
SQL Server 2005 Service Pack 2 2005.90.3042
SQL Server 2005 Service Pack 3 2005.90.4035
http://support.microsoft.com/kb/321185
How to determine which version of SQL Server 2005 is running
To determine which version of Microsoft SQL Server 2005 is running, connect to SQL Server 2005 by using SQL Server Management Studio, and then run the following Transact-SQL statement.
The following results are returned:
For example, the results resemble the following.
9.00.1399.06 RTM Enterprise Edition
The following table lists the Sqlservr.exe version number.
Release Sqlservr.exe
RTM 2005.90.1399
SQL Server 2005 Service Pack 1 2005.90.2047
SQL Server 2005 Service Pack 2 2005.90.3042
SQL Server 2005 Service Pack 3 2005.90.4035
Here's a pretty comprehensive page on figuring out your version in a variety of ways.