Thank you - that did it!

"Tools" Drop down menu in main window.
Select "Media Tree" under the "Library" heading.
Place a check next to "My Computer."
Click "OK."

Somehow I've lost the "My Computer" or "This PC" that used to show up as part of the "Media Tree" left hand column display. From there I could locate digital music files not in my MM Library and drop them on my iPod (which still shows up when I plug it in). I've looked at all the MM View options but nothing, so far, has gotten those elements back on my Tree View.
What am I missing?
Thanks.