In order to create a Linux boot disk while on Windows, you need to use a program like Rufus (see next slide)

In some revisions of Windows 10 the OS by default will use all 4 of the Primary Partitions to make it harder for you to leave Windows

https://askubuntu.com/questions/149821/my-disk-already-has-4-primary-partitions-how-can-i-install-ubuntu

When changing any OS you should back up your data. Try saving it to an external SSD

Tricks To A Linux Install