Hey toddadd. I have just tried your method with on the same model touch panel display. The drivers do install successfully, but I am still not getting any response from the TY-TP42P8-S.
What I did:
Set up a test machine with windows 7 32 bit. Plugged in the usb cable, downloaded the driver and extracted to a folder generated on the root of C (lets call it C:\Folder\), opened up device manager, right clicked on the first usb unknown device and clicked update driver. I looked through the folder C:\Folder\ and let the subfolders be searched too. The driver Matsushita serial bridge installed first. Tried the touch panel, no response. Saw there was another usb device that was unknown. I right clicked on that device and clicked update drive looking through the same folder and letting the subfolders to be searched too. The device got installed properly. When testing the touch panel again, no response. This is with both pen on and pen off.
Could you quite possibly provide a more in depth description on what else you might have done to get this to work?
Thanks again.