When you select an experiment to run, MediaLab needs it to be a traditional file path such a "c:\my experiments\experiment1" or "g:\network\shared\experiment1" etc. If the Parallels program does not give Windows drive letters to use by default, then you can probably ask Windows to create them.

Try this..

Open any folder and see if there is a command on the Tools menu to "Map a Network Drive". It should allow you to choose your experiment folder from the desktop and assign it a letter like "E:" or "F:". Then, when you go to select your experiment, you should see the drive letter as an option--click it and then choose your experiment from there.