Acer Iconia W510 Tablet problems, booting - password

Hello everybody!

I got a Acer Iconia Tab W501 from a friend of mine, who got it from his father that passed away

He told me that he would like to reset it completely, then sell it because he needs the money, so i said that i possibly could help him with that.

The problem:

I entered the BIOS, turned off secure boot, and enabled F12 booting, also put the USB Drive on top of the list.

But,

Even though i have a copy of Windows 10 on the USB it wont show up in the boot order list, i've tried formating with different programs and in different formats, nothing helps.

I tried to restart the Windows 8 that was installed it, while holding shift button which got me into the Advanced Start section, went in to troubleshoot, tried resetting the Windows there, but it asks me for password.

Tried to enter the Command Prompt, still asks me for password.

Whatever i do, it asks me for the password that is installed on his fathers account, which he didnt pass on before he died, ofcourse, who would have thought of it...

We tried a couple of different passwords, the hint didnt help.

Think i have tried everything, but nothing has solved the problem.

Does any of you have any ideas?