Thank you so much Rog!!! In fact I couldn't thank you enough.
This seems to work just fine. I had to download an evaluation copy of Forte to check it out since it doesn't seem to be included with PT12.
After some fooling around it would appear that if I want to use another synth in addition to Forte I need to set each individual track to the desired synth in order to avoid a rather strange response. Setting all tracks to Forte and then adding another synth to one track (ie Crystal) will result in all tracks becoming the second synth, but that's another thing to investigate.
I think I will be updating my Powertracks in the near future and then getting a new audio interface to plug in an instrument/mic via usb. Then I'll have a portable setup, which is what I wanted.
After purchasing a new laptop with very nice advertised specs ( Intel Core i7, nvidia graphics etc etc) it is rather disheartening to learn that these machines can be so sadly lacking in the audio department.
Thanks again for your wonderful responses and advice on this problem!
Terry