Install Linux on existing multiboot system without messing up drive letters

Install Linux on existing multiboot system without messing up drive letters

I've finally gotten my multi-boot development system (WinXP, Win7x86,
Win7x64) booting properly so that no matter which OS boots, it boots as if
OS is C: and there is a D: for scratch / sharing between OS's.
I now want to add Linux to the mix but I don't want to mess up the fragile
grasp the Microsoft OS's have on their drive letter identity being C: no
matter what. (In case you're wondering, to get them all to recognize
themselves as C: you have to install WinXP first, then Win7x86 then
Win7x64.)
I don't have another terabyte drive to image this to in case I mess it up
so I don't want to guess at the proper procedure.
Can I simply install Linux (Mint 15 Cinnamon is what I'm going with) and
let Grub take over managing multiboot? If the Microsoft OS's don't retain
their drive letters as C: when booting, I have to start over.