To install .NET Framework 3 in offline mode on Windows 8, you need your installation iso / flashdisk drive with the windows installation or windows installation cd, then type this on Command Prompt with admin
Dism /online /enable-feature /featurename:NetFx3 /All /Source:F:\sources\sxs /LimitAccess
type the drive where your windows installation is located, for my case it’s in drive F.
Give it a try 😀
I always forgot how to register .Net in IIS so i will write it here
The following command installs the ASP.NET version associated with the tool and updates the script maps of all existing ASP.NET applications. Note that only applications that are currently mapped to an earlier version of ASP.NET are affected.
type this in command prompt
for full information can be seen in http://msdn.microsoft.com/en-us/library/k6h9cz8h%28v=vs.71%29.aspx