Installing a windows 10 OS on a previously used SSD; Do I have to format the previously used SSD?

Solution 1:

The installation disk will reformat the disk for you - as part of the installation process, by default on almost every mainstream OS. If you're doing something hipster like haiku, or a more 'basic' install like gentoo does you might need to, but with Windows 10, or more mainstream linux based OSes, you should be fine.