How to install windows after Ubuntu?

Question

Windows

I have two Ubuntu 20.04 and 18.04 operating systems on my PC, how can I remove them and install Windows?

Answer 1

You make a bootable Windows flash drive, boot from it, during installation you demolish partitions with Ubuntu, partition the disk as you need and continue the installation.

Answer 2

Run from any LIveCD of any Linux. Open terminal. Run the command:
dd if=/dev/zero of=/dev/ada0 bs=512 count=
where /dev/ada0 is your disk
. As a result, you will get an uninitialized disk.