Ghost 14. Dont show any saved data in pie displey in backup display window

In my Norton backup display window I see in the pie shaped display brown as my free space and in blue I see other used space and in green nothing. I have always see green as my backup data also when I look at MY COMPUTER it shows  my Free AgentGoFlex drive  (which I use as my backup drive) as L: on my Norton backup display window it shows as M:    What’s happening???