When I tried to turn on the .NET 3.5 Framework in my Windows 8 box, it returned me this error code – 0x800F0906
Per KB2734782, the metadata for features on demand are included in Windows 8, but the binaries and other associated files are not. So Windows by default tries to download it from Windows Update website when you turn the features on. But if the system have problems to access internet, or the system updates are controlled by WSUS or SCCM, it will return the error.
The simple fix is to insert the Windows 8 installation CD, and run the command to install from local source:
Dism /online /enable-feature /featurename:NetFx3 /All /Source:D:\sources\sxs /LimitAccess
Jackie Chen's IT Workshop 