When I run 
Dism.exe /online /enable-feature /featurename:NetFX3 /All /Source:C:\sources\sxs /LimitAccess 
after 65.8% it says Error 0x800f081f 
the source files could not be found. 
Use the /source option to specify the location of the files that are required to restore the feature.

Also my windows misses Specify settings for optional component installation and component repair option.

What else can I do ?

Click the following link and read the post that I wrote earlier. Hopefully it helps you.

http://social.technet.microsoft.com/Forums/windows/en-US/2860e2d3-ab9b-4a9c-b8e9-fd0518fcda22/enable-net-framework-35-in-win8-without-mount-iso-file?forum=w8itprogeneral

• Edited by T. Kujala 17 hours 42 minutes ago

Click the following link and read the post that I wrote earlier. Hopefully it helps you.

http://social.technet.microsoft.com/Forums/windows/en-US/2860e2d3-ab9b-4a9c-b8e9-fd0518fcda22/enable-net-framework-35-in-win8-without-mount-iso-file?forum=w8itprogeneral

• Edited by T. Kujala Thursday, January 23, 2014 6:05 PM

Hi,

Please refer to the link below which talk about install .net 3.5 in Windows 8, 8.1.

Installing the .NET Framework 3.5 on Windows 8 or 8.1:

http://msdn.microsoft.com/en-us/library/hh506443.aspx