Windows 7: Switchable Graphics Intel 4000 Drivers Installation

Hi guys,

I am Technician who works on various dell Systems.
All the New Dell Systems that I receive I have seen a common issue on them
If they Have switchable Graphics On it
Intel HD 4000 and AMD 7760M
I Reinstalled Windows On the System and there were 2 Bangs Under Device Manager for Standard VGA Adapter.
I tried Installing the Intel HD 4000 Video Drivers First and it Failed and gave a message that the Drivers did d not meet the min requirements of the System
I downloaded the latest from the Intel Website 64 Bit drivers
So after this message I went Ahead and Installed the ATI 7760m drivers and they Got Installed Perfectly and after restart the Intel 4000 Drivers also got Installed Perfectly.
So I failed to Understand Why it Happens
Prior to this On any machine that had Switchable Graphics we had to install the Intel Drivers frist and then The Discrete card drivers
anyone who Can throw some light on the logic behind it?