This is not a Unix question, though I can see why you think it is. You do not have to tell the installed OS about it.
How things work:
- Computer is switched on.
- Computer starts running program in boot ROM (often mistakenly called BIOS, on PCs).
- ROM based boot-loader, loads 2nd stage boot-loader from disk (or USB, or …).
- 2nd stage boot-loader, loads 3rd stage boot-loader from disk (or USB).
- 3rd stage boot-loader, loads operating system kernel and init process.
- init process loads the rest of the operating system.
- Operating system loads video player.
- Video player loads minecraft videos.
- User watches minecraft videos.
As you can see, the operating system does not load another operating system (except it can load a virtual-machine). The solution to you problem will be in the boot loader settings (often labelled bios settings).