^ exactly how were you formatting it? As stated above deleting partitions and creating new ones, or just formatting the existing partitions have nothing to do with the bootloader that might be on there.
This is not a windows install that will overwrite the bootloader on install
Linux and bsds don't assume just because your installing them that they should overwrite an existing bootloader.. You would have to specifically do that! Now some installs might ask, etc. But others that have been trimmed down to just install a specific distro might not.
Wipe the zero track and you should be fine on install of whatever new OS you install - as you "tinker" with different OSes you will find this out. Or just use VM for your tinkering and then you don't ever have to worry about it, because you can just create a clean new virtual disk for all your different installs