The location for the Respondus Projects folder is specified at the time the software is installed, usually the user's Documents folder on the local drive, "C:\Users\{user_name}\Documents\".
If the location of this folder is changed after the installation of Respondus 4, go to File-> Preferences-> General tab and then "Update" the location of the Respondus Projects folder.
Alternatively, you can reinstall Respondus 4 and specify the desired location when prompted.