SQL 2008 Cluster. NET Framework 3.5 error

Hi

I am installing SQL 2008 in Host Clustering and Guest Clustering
See: http://santospardos.blogspot.com/2009/01/hyper-v-performance-cluster-hyper-v_08.html

My first fall when I starting to work:
Error: SQL Server 2008 Setup requires Microsoft .NET Framework 3.5 SP1 to be installed.

If the W2K8 is clean (nothing installed), the SQL wizard runs well.

My server belongs a lab environment. The server has many things installed.
I tried to install NET Framework 3.5 SP1 with the installer downloaded from Microsoft Website.
I have NET framework 3.5 in the server and I have the same error. (see picture

Solution:
I installed everything from the DVD bye my self.
DVD:\x64\redist\DotNetFramework\dotNetFX35Setup
DVD:\x64\redist\Windows Installer\x64\INSTMSI45

Santos