New Dell Inspiron 3471 - factory Windows installed - duel boot with mint 19

Asking advice: Installing mint-19 along side factory installed Windows-10. UEFI is turned off so other operating systems will boot. I have set up multi-booted operating system. However, it's always on older BIOS machines and I was never concerned whether or not Windows survived. This new machine is for my wife and she wants both Mint and Windows. I'm under the gun and require reassurance and guidance. Thanks for your help.

cheers :-)