1. Updating your BIOS, Checking if you have UEFI and SecureBoot, Checking your Product Key from your UEFI BIOS or COA
Dell Drivers: http://downloads.dell.com/published/Pages/index.html
Windows Product Key Tool: https://neosmart.net/OemKey/
RWEverything: http://rweverything.com/
Written Guide BIOS Update and Checking for UEFI and SecureBoot
Written Guide Notes on the Windows 7 and Windows 8.1 Product Keys
2. Downloading a Windows 10 TH2 OEM and Retail .iso
Windows 10 Media Creation Tool: http://www.microsoft.com/en-gb/software-download/windows10
Windows 10 Direct .iso Download Links: https://www.microsoft.com/en-us/software-download/techbench
3. Clean Install Windows 10 TH2 from a Bootable USB
4. Installing Systems via Windows Update, Checking your Model, Checking your Hardware IDs and Driver Versions in the Device Manager and Downloading and Installing System Drivers from Dell
Dell Drivers: http://downloads.dell.com/published/Pages/index.html
Written Guides Notes on Checking the Hardware IDs in the Device Manager
Written Guide Notes on Recommended Driver Installation Order