Dual boot Win/Lin on separate HDs with a switch - bypass Grub?

[DeepThought]

It sounds like grub was installed to the mbr of your linux hdd and controls all boot functions.
You will need to recover the windows bootloader on the windows hdd.
Hope this website helps in that:

Code:

https://www.nextofwindows.com/how-to-manually-troubleshoot-and-repair-windows-7-bootloader

Don't forget to switch off your linux hdd before following the instructions to repair the mbr on the windows hdd