XXHighEnd

By means of the field concerned in the Settings Area, you can denote something like
h:=q:
meaning that what ever before has been drive h:, now is called drive q:. Not that you can change Drive Letters by this, but this is to be looked at the other way around : within some OS you called a drive h:, and within another OS (think Dual Boot) that same partition (or disk) is now called q:.
The importance - or conveniency will jump at you when you use Galleries, which actualy consist of references which are a kind of "hard" registered in the music folders.

You can mention as many of these "substitutes" as you like, and also you are allowed to re-substitute the above example like this :
q:=j:
So, first your h: became a q:, and lateron this q: became a j:. Notice that this comes handy when you used q: as your new Drive Letter for some longer time, created new Galleries during that period (all referring to q:) while again later your partion/disk has become j: for whatever reason. So now *and* h: *and* q: have turned into j:.
When you never used q: at making Galleries, you can obviously just replace h: with j: at once (h:=j:).