Sometimes when you try to install .Net 3.5 on Windows 2008 R2, you would get an error message:
You must use the Role Management Tool to install or configure Microsoft .NET Framework 3.5 SP1.
To get around this, right click on computer, select manage. Select Server Feature node and add a new feature. The first one on the list should be .NET 3.5 Features. Install that and voila.
I need to install .Net 3.0 and 3.5 on Server 2008 R2. I noticed that when I look to add features in Server Manager I only see .Net 3.5. If I install .NET 3.5 will that include the 3.0 Framework also?
Yes, installing .NET 3.5 should get you everything in .NET 3.0.