I can't help with the installation of the Picture Motion Browser software, maybe someone here will come along with the answer to that or maybe even Sony Technical service department will help.
I was just going to suggest a possible workaround to the problem. Do you want to get the video on the computer to be able to edit it, I'm assuming that's why you want to use the Picture Motion Browser software as you can see the video I guess by playing in a DVD player or on your computer by putting the mini disc in your DVD rom drawer on the pc.
If I'm right and it's just for editing purposes you want to get it on to the pc you could download a free trial version of a video editing programme that will work with DVD discs as most video editing programmes do. An easy programme I use sometimes is Arc Soft Showbiz DVD free 15 day trial here
But there's plenty of other video editing programmes with free trials that will work with dvd discs from camcorders and perhaps do a better job than the manufacturers bundled software.