If you're like me and you're trying to run some applications that rely on .NET Framework 2.0 - 3.5 on Windows 8, you might be surprised to find out that it's a separate install. Instead of spending time trying to download that feature off the web, the easiest way to go about it is to insert the DVD or mount the ISO on your Windows 8 client. You can run the following command and it will take care of installing the legacy versions of .NET for you. This command needs to be run from an elevated command prompt.
dism.exe /online /enable-feature /featurename:NetFX3 /All /Source:X:\sources\sxs
Substitute your appropriate drive letter in place of X: for it to work. The install will take around 10 minutes, depending on the specs of your computer.
All credit goes to a member of Anandtech forums. The original thread can be found here.