serialtest.py is hardcoded with the port for Linux/Unix systems.
Are you sure that the image is being referred properly, if your file name contains spaces you need to escape them properly for the Windows shell to recognize.
Are you using the most recent version? I have added several changes to my repository that have not been integrated yet to "upstream".
To use the updated graphical interface you need to have PyQt4 installed as well as all of the requirements in requirements.txt.
I will release a Windows 64 bit standalone bundle next week.