Like "D:|" or "D" etc.
%R in the tab name will turn into the drive letter, e.g. C:.
You can use %R| if you want C:| in the name, although beware if will do strange things in virtual folders and e.g. display Desktop| in the Desktop folder.
Built-in things you can do with tab names are documented here.
For more esoteric things, you can use a script add-in like this one:
%R just used to rename a folder name, I want to set it as default, the script must be useful.