Fix dot net framework 3.5 in windows 8/8.1

If your computer is not connected to the Internet, you are using a local network source, but the network location is inaccessible or doesn't contain the right files. You may receive an error message like the following:

“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.”

In this case, you should check your Internet connection and retry the operation. If you cannot connect to the Internet, you can enable the .NET Framework 3.5 .NET Framework 3.5 by using the Deployment Image Servicing and Management (DISM) command-line tool and specifying the installation media (ISO image or DVD or other external drive) you installed Windows 8 from.

In windows 8 or 8.1 , launch  command terminal as administrator  then run the following command - 

DISM /Online /Enable-Feature /FeatureNmae:NetFx3 /All /LimitAccess /Source:D:\sources\sxs

here D: is your installation media where you have booted your windows 8/8.1