Microsoft on the whole has done an excellent job of including all the device drivers your computer needs to function properly when evaluating the Technical Preview builds. Open Device Manager and you will see what I mean. The one significant exception with the 9879 build is for user’s who have an Intel X99 chipset (Blue screens and other issues).
In the past Windows editions such as XP, Vista, 7, 8.0 and 8.1 required that to upgrade from one version of Windows to the next you had to manually download the drivers and store them on external media, perform the upgrade and then install the drivers after upgrading.
Making matters worse is the fact that if you purchased a computer from one of the major PC manufacturers such as Dell, HP, Acer, ASUS, Toshiba and others there may not be any drivers listed on their support web site if for instance you want to upgrade from XP to Windows 7 or to Windows 8. The same is true when upgrading from Vista to Windows 7 or Windows 7 to Windows 8. The lack of driver support can kill your desire or ability to upgrade and has been a constant road block when trying to upgrade to each new version of Windows.
The plain truth is that most computer manufactures do not develop new drivers for the latest version of Windows for older computers they have sold; drivers are only available for the version that came with the computer when you purchased it. In some rare instances if for example a user purchased a late model PC with Vista installed (late Summer / early Fall of 2009) and the same model was sold with Windows 7 when it was released in October of 2009 then you have a cross over model that may have both Vista and Windows 7 drivers available.
The other longer term issue is that the days of Service Packs are no more as Microsoft now sees incremental versions like Windows 8.1 and 8.1 with “Update 1” as the way to patch flaws, neither of which included drivers updates. Even Windows 7 Service Pack 1 did not have any driver updates that I’m aware of as after installing Windows 7 (with or without SP1) still required installing device drivers on any older or new computers or motherboards.
So the big question is: When Windows 10 is released late next year will it include all the drivers you need to upgrade or will Microsoft strip most of them out and leave it up to the computer, motherboard and graphics card manufactures to develop the drivers?