..... I try to create an ISO output file, ... nearly at the end .... I am trying to create the output on my USB external hard drive with plenty of spare capacity.
I have tried to create an executable file and that also crashes when getting to the end of the process.
In desperation, I have transferred all the files and software to a friends Laptop and it runs OK and produces the output - albeit rather slowly.
Finally, does Proshow Producer create a log file after crashes ?
I've never attempted to create an ISO file on an external drive. So, maybe this is the problem. ProShow used to have problems with external drives in general, in the past. I'm not sure if this is still the case with the newest versions. You are not saying if your friend was successful with an external drive too, or if he made the ISO on an internal drive.
Another reason for the crash, could be a faulty file that ProShow may have problems with. For example a gif (if you are using any), or even one of the video clips or the audio files.
What is in that slide, near the end, where ProShow crashes?
I'm not aware of any crash log in ProShow.
Try creating the ISO file on an internal drive, if you can. If it fails too, then try eliminating problematic files.