I was trying to setup SQL Server 2008 on my lab machine running on Windows Server 2008 R2. When the setup was installing the prerequisites, the following error message popped up.

This is a very simple error message, which a DBA would come across often. However the next screen which popped up after this message was interesting.

Since Windows Server 2008 R2 has the .Net framework 3.5 already available as a feature, all we need to do is just enable that feature. There is no need to download the installer and install it separately. As the error message states, just enable it using the “Role Management Tool”. Role Management tool can be found under Server Manager –> Features –> Add features as seen in the following screenshot.

That’s all. Now the .Net framework 3.5.1 is installed and ready to use! After this the SQL Server setup completed successfully.