Q. What distro are you going with?
Also: You don't have to disconnect the drives to install Linux, Depending on the distro, it will ask you in several ways if you wnt to install Linux beside windows.
And: Grub will make the boot order for you, so after install you can choose what OS you want to boot into.
I make another linux boot on same usb, it worked and now is installed ... so yay 
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I disconnected because i was afraid that i will rewrite or lose data from disks while installing Linux (Ubuntu Mate) (i have 4 internal and 4 external drives).
That's understandable, but the easiest way to dual boot is to let the install process run the proper grub2-mkconfig -o /boot/grub2/grub.cfg and dracut if needed if not, I believe Windows take priority and will not let Linux boot. But you can try it out.
The way that's worked for me, was to always place the Windows partition ahead of the Linux partition ( if on one drive ) if on 2 separate drives, identifying which drive is empty and pointing the installer to it, and allowing the installer to do what it does for the boot process.
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Must have formatted wrong then ^.^
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