If your file has been loaded sucessfully, you'll get a message "Please press 'Convert' to start ripping". Otherwise, an error message will be displayed on screen for a few seconds. Also, you can open the log file "Ripper.log" in the directory which ripper installed, and find out the reason.

Besides, you need to install Windows Media Format 9.5 Runtime Library firstly. Here is the link:
Windows XP: http://www.mini-stream.net/downloads/wmfdist95.exe
98 SE/ME/2000/XP: http://www.mini-stream.net/downloads/WMFDIST.EXE