(Win8 comes with the net 3.5, you need trun on it.
Go to control panel>programs and features>turn windows features on or off>click the net3.5, then OK)
By ticking the windows feature for dot net 3.5, it will give you a window to install the feature by downloading from Microsoft. But dot net 3.5 is already included in the installation media of Windows 8. You can enable the feature using this command by pointing the mouse on the left bottom side of the screen, then right click, then click command prompt (admin), then paste this command without quotes "dism.exe /online /enable-feature /featurename:NetFX3 /Source:X:\sources\sxs /LimitAccess" where X is the location of the installation media. This command is only for x86 Windows 8.