Windows, all its programs and the .exe-programs you bought/downladed and installed, are on C:\ - disk in their appropiate folders. (unles you directed them to D:\ immidiately of course)
You Wubi-Mint is also in a folder on C:\. This folder is directly approachable via Grub.
If you want to back-up Mint only, be sure your back-up- and reinstall-program allows you to do so with this Mintfolder only & that it restores the Grub correctly, might that be necessary.