We recently rolled out an image for Windows 8.1 for corporate use. Unfortunately some of the products that I use require .net 2.0+ to be installed. I remember from my Win7 days that I can simply go to Programs and Features, and then turn Windows features on or off, then select .net framework 3.5 (includes 2.0 and 3.0).

Unfortunately I was receiving the following error:

0x800f0906: “Windows couldn’t connect to the Internet to download necessary files. Make sure that you’re connected to the Internet, and click Retry to try again.”
0x800F081F: “The changes could not be completed. Please reboot your computer and try again.”

Dang. Work around (Thanks J3 and http://msdn.microsoft.com/en-us/library/hh506443(v=vs.110).aspx)

Mount the Windows Installation Image
Either pop in your windows 8.1 CD or double click on the ISO (running Windows 8+ allows you to mount ISO by double clicking, win7- needs some sort of ISO mounting kit)

Command Line Install
Open a command prompt with Admin credentials (run as admin if necessary)
DISM /Online /Enable-Feature /FeatureName:NetFx3 /All /LimitAccess /Source:d:\sources\sxs

Explanation Of Arguments

/Online targets the operating system you’re running (instead of an offline Windows image).
/Enable-Feature /FeatureName:NetFx3 specifies that you want to enable the .NET Framework 3.5.
/All enables all parent features of the .NET Framework 3.5.
/LimitAccess prevents DISM from contacting Windows Update.
/Source specifies the location of the files needed to restore the feature (in this example, the D:\sources\sxs directory).