Red X on tray icon, unable to access removable drive

Using XP Pro SP 2 and all fine until today.  The removable drive was on "F:" and is now on "G:"  This should be an easy fix but I can't remember how to reassign the drive letter on the removable drive I am using as my backup.  I think that is why there is a red X on the Ghost15 tray icon.  When I open Ghost15 through a shortcut, it cannot locate the backup.  The screen says "this program is unable to connect and communicate with the Norton Ghost backup service on [name of computer]. Thanks in advance.