try this - set a folder icon to the icon you want the windows drive (can be any folder anywhere). Enable "show hidden files" (using terminal or Cocktail's free trial) then inside that folder should be an externsionless "Icon" file. Copy that to a thumbdrive or a cd anything that's readable in Windows.
Boot into Windows
Copy the "Icon" file to the root of the C: drive (you might have to enable hidden folders)
In "theory" this should work. The FAT32 thing does would with thumbdrives.