open the directory with all of the folders, goto View and make sure Status Bar is checked and then select all of the folders you want counted and down at the bottom it will say how many you have selected

I also have a large library of music. I keep it in a folder called Library. Here is what I did. I right clicked on the folder named Library and selected properties. Properties shows how many files and how many folders. I have a folder for every artist such as Bob Dylan or Jimi Hendrix. Within each of these folders there may be only one or several different folders, one for each disc. If a album has two different discs for instance I will have two sub-folders underneath the folder for the artist. Anyway, I knew that I have a folder for every artist and that the folder with the artist's name on it does not have any music in it. It has any number of subfolders that contain the music. So I wanted to subract the numbers of folders with no music in them. To do this I simply opened the folder in Windows explorer and looked at the status line at the bottom of the window. It told me how many folders I have at the root of my Library folder. This is where each artist's folder is. I then subracted the number of folders on the status bar from the number of folders shown when I got the properties of my Library folder. Now I know how many CD's I have ripped into my Library folder. I hope this works for you.