DO I HAVE TO BUY WINDOWS 10 MINECRAFT AGAIN ON MY NEW COMPUTER?

Help on my old laptop I got minecraft on the app store but now my computers broken and I can't play it. I got a new computer, I have the demo version of it but my dads account got it. I logged into my account that i bought minecraft with but I still have to pay! I even logged into the xbox account but I still can't play it, what do I do?

The Windows 10 version of Minecraft is PERMANENTLY TIED to the Microsoft account (which the Windows Store runs on) that it was redeemed on. If you purchased the game on somebody else's account (like your father's, as your post suggests), you will either have to get logged into that person's account on your computer (which gets into some nasty personal data entanglement) OR purchase the game through the Windows Store on your own account.

Even if you log into the same XBox Live account, all that does is provide online support of the game. The DRM keys would be stored on another linked account.