MC does alot well but Library managment not so much, plain sucks actually.
Hilarious! It's one of the things it does best. As requested above, tell us the directory structure you have and the path you wish to migrate to.
Let's say you have everything in C:\Users\XYZ\Music\ (For now ignore the subfolders of artists or albums you will have under the Music\ directory)
And you wish to move it all to D:\Music\
I'll use these locations as examples, and you should be able to substitute in the actual paths you have to make the general process outlined below work for you:
Select all the files you wish to move in Standard view
In Tools > Library Tools > Rename, Move and Copy files, select the option starting with "Update..."
Uncheck the first two options, but check the Find and Replace option.
Then simply:
Find
C:\Users\XYZ\Replace with:
D:\When you do this, MC will look for all your music in D:\Music directory, but preserving the subfolders structure you had before.
However, since we used the "Update" option, it won't find anything there because the files haven't been moved yet.
Now simply go to Windows Explorer, and COPY the C:\Users\XYZ\Music\ directory to the D:\ drive.
MC should now find all your files, and any that were not part of the library will have been moved with the music too, exactly as before.
Once you've verified all worked, you can delete your original Music folder.