(The following is a very long tedious discussion of my struggles with this problem. I apologize to anyone who reads this and wonders why I spend so much time discussing this problem. I would suggest that only people who are struggling with this activation problem take the time to read this although I suspect that my friends grandpaBruce, Larry and Richard fdisk, who have made many useful suggestions, will also read it.)
I thought Larry's suggestion was excellent. I don't use a standard (for my system) setting of 96 dpi but use a custom 144 dpi. But now I can't verify if this would have worked (manually activate the MPEG2 codec).
Here's what happened. A day ago I decided to install the new Roxio Creator 2009 that I purchased a week ago from Roxio. I was reluctant to do this because the subprograms of EMC9 that work work quite well, as I mentioned in an earlier post in this thread. This new C2009 worked well and EMC9 also worked well in the functions in which I use it: copying discs, recordnow, a few others. This seemed a good solution to me: use EMC9 where it does work and where I am used to it, and use C2009 in other uses involving video.
But after seeing Larry's suggestion I went to the standard 96 dpi and tried a video function in EMC9. And before getting the message that my MPGE2 codec needed activation it said that I had a bad installation. Although I had uninstalled and reinstalled EMC9 a few days ago (at Richard fdisk's suggestion) this was the first time it had told me that I had a bad installation.
I then went back to my custom 144 dpi - no change.
I then uninstalled and then reinstalled EMC9 and to my surprise everything worked: it never told me that I had to activate my MPEG2 codec! I could have left it like that but didn't think that was fair to myself or to others who might be struggling with this activation problem.
I then completely uninstalled EMC9 and C2009, trying to make a fresh start as if I was a new user.
I installed EMC9 and, again, everything worked. It never said that my MPEG2 codec needed activation.
I then installed my C2009 and it works fine, as does EMC9.
What can I conclude from this? When I installed C2009 it made one or more changes to my system which were not undone by the uninstall of that program. (I can prove this easily. When I first installed C2009 I had it play a dvd movie (a Woody Allen movie named "Alice.") After completely uninstalling C2009 and then reinstalling it and then testing it with "Alice" the program asked me if I wanted to continue this movie from where I had stopped it the last time I was playing it and when I said yes, that was what it did. So some information is retained on the computer across an uninstall followed by a reinstall.) I don't know what these changes were but apparently they were sufficient that EMC9 no longer asked me to activate my MPEG2 codec. (As was pointed out in other threads on this topic in the Roxio forum the new versions of Roxio, including C2009, never ask for this activation.)
So I have both programs (EMC9 and C2009) installed. Both work fine. I am never asked to activate my MPEG2 codec. But I can not verify Larry's suggestion to use the standard 96 dpi in order to see the 25 digit code required for manual activation of my MPEG2 codec.
My thanks to everyone who made suggestions concerning this problem.