You can easily determine your CD key for your SQL Server software by just typing a few lines into the query window. To do this:
1. Open up the query window.
2. Copy and paste the following:
USE master
USE master
EXEC xp_regread 'HKEY_LOCAL_MACHINE',
'SOFTWARE\Microsoft\Microsoft SQL Server\80\registration',
'CD_KEY'
3. Execute the query.
The results will give you the CD key under the Data column.