If You make the page as Hide defaults on the unattended setup it does'nt ask serial key at the time of your installation You can directly download the addon for.netfx 3.5 or yoc can create manually addon of netfx 3.5 Download the Virtualtek addon integrator of nLite Make a cab of netfx 3.5 Choose the Silent mode as based for u'r installation integate through nLite start the process This ideas make better for u