First, Look at the Terms and Conditions of Windows 10: https://www.microsoft.com/en-us/Useterms/Retail/Windows/10/UseTerms_Retail_Windows_10_English.htm It doesn't mention ANYTHING about being able to access the BIOS or UEFI Firmware, and my proof for it changing the Firmware of the computer, Is: Exhibit A: On a UEFI System, Open Device Manager, You'll see the "Firmware" Directory, If you open it and right click it, You'll see the ability to CHANGE the System Firmware from INSIDE of Windows, Even though it DOESN'T mention it in the Terms and Conditions, This proves that Windows is able to do it by itself. Exhibit B: This one isn't exactly solid proof, But while I was fixing a device called A "PC2GO" from 2013, made by Hipstreet, I reinstalled Windows 10 on it, Turns out the problem was the CPU being overclocked, Small PCs like the PC2GO have problems with that. (BSOD, Windows 10 not booting at all, etc,) Overclocking the CPU is a setting being changed in the BIOS, So reinstalling Windows 10 should NOT have fixed the problem unless it changes the BIOS during the Installation.