As part of an operating system deployment task in System Center Configuration Manager 2007 R2 (SCCM), I needed to enable the .NET Framework 3.5.1 Feature on Windows Server 2008 R2. I thought it would be easy to do this as part of the task sequence, but it proved trickier than I expected.
I added a “Run Command Line” step and entered the command “Dism.exe /online /Enable-Feature /FeatureName:NetFx3 /LogPath:c:\Dism.log”. On its own this isn’t enough for the feature to be enabled. you must also tick the “Disable 64-bit file system redirection” in order for the feature to be enabled.