Dualbooting on filled disks
This section will explain how to deal with disks with data already in use in them for dual booting. This may seem difficult, but it's quite simple, just remember to backup all of your data before starting. This section has destructive and non-destructive methods of manipulating partitions, disks and data.
This section is meant for those who have disks with an OS installed on it already, or just a secondary disk with partitions other than OSes. To be honest, either way, they both follow the same idea and procedures, but just to help with some special cases, it has been decided to split them into two different categories.
Let's get started...