Okay, here's what I want to do. I have KaOS already installed on a 1TB hard disk. I have no interest in wiping and re-installing, although I know it's easier to start with Windows and install Linux after. I have a 500 GB hard disk I would like to install Windows 7 on.

How do I go about this in such a way that 1) I don't destroy my Linux install, 2) Linux Grub retains control of the boot menu and 3) KaOS is the default in Grub?

I believe Windows 7 can be installed on a secondary HDD (more info here). In this case there wouldn't be any problem in plugging the 500 GB as a secondary (slave) drive.

I'm not familiar with KaOS, but I think this might help you get Grub2 to boot Windows 7.

edit: Forgot to tell you to unplug the 1 TB HDD before installing Windows 7 to avoid Grub being overwritten by Windows. (This can be solved afterwards, but you'd need to boot from a Live system.

In addition, you will probably need to run some command to update the Grub configuration to include Windows 7. Not sure about KaOS, but on openSuSE it's necessary to run update-bootloader --refresh in order to include other OSs in the Grub menu.

Disconnect the drive with Linux on and install windows to the 500GB drive.
When finished, re-connect the Linux drive, set it to first boot priority in the BIOS, boot it up and update Grub to add windows to the Grub menu.

That worked slick! Thanks, guys.