Multiboot setup question

[Orionaut]

Does anybody have a a link to an easy set up for multiboot?

Google searching hasn't been very helpful, I have two versions of WIN10 on separate disks (And old and a new install) I also want to have a version of Win7 (For old games that wont run under win10) and Linux on separate disks too

Basically imagine a set up where I already have four OS on four separate independent disks already installed but I want to add a multiboot menu with a default preference if I do not make a choice on startup.

 

[Buffalo2102]

The choice is whether you use the BIOS to choose which disk/OS to boot to, or you use a boot manager.
You can set the default boot device in BIOS and if you want to boot something else, you can usually just press a key (F11 on my board) during boot to choose a different OS.
It looks like a boot manager might be best for you. REFInd is probably a good place to start http://www.rodsbooks.com/refind You can install rEFInd on a USB stick and boot to that, to try it out without having to install anything.
Alternatively, you could use the GRUB bootloader on your Linux disk.