From KB 955392 there’s lot of info there, but the quickest “one time” install
method is to follow “Procedure 1: Basic slipstream steps”
1. Install the .NET Framework 3.5.1 feature
2. Download the SQL SP1 service pack
[http://www.microsoft.com/downloads/details.aspx?FamilyID=66ab3dbb-bf3e-4f46-9559-ccc6a4f9dc19&