Should I have to activate Movie studio23 platinum every time I open it. And why have all my .avi files had an extra file .hdp file which is Magix sound editor file when I dont have Magix sound editor on my PC. I am using Windows 10.
Should I have to activate Movie studio23 platinum every time I open it
No. But something is preventing the registration/activation becoming permanent, perhaps your firewall or antivirus? Do you see a message confirming that activation is successful and suggesting that you keep your serial number safe in case you should ever need to reinstall the software? There should also be another screen which follows, which usually invokes the User Access Control (so requiring a "Yes" answer); I believe this is what actually "saves" the activation data to your PC.
And why have all my .avi files had an extra file .hdp file which is Magix sound editor file when I dont have Magix sound editor on my PC
Actually, you possibly do have Magix Music Editor installed (as part of the MMS installation) but those .HDP files are simply the ones which control the graphics of the waveform which you see on the MMS Timeline.
. . . . Actually, you possibly do have Magix Music Editor installed (as part of the MMS installation) but those .HDP files are simply the ones which control the graphics of the waveform . . . .
Music Maker does not have to be installed - Movie Studio creates 2 support files for video and audio the .HDP file and a .H0 file which contain the video and audio graphics and audio waveform.
I see the message confirming activation is successful and after that the a screen asking if I want to allow this app to make changes to my machine. Clicking yes opens the programme.
I have tried turnng off my Norton firewall but the same thing happens. Do I need to uninstall and then reinstall.
So it seems that the all-important data about the registration is not being correctly saved. I assume this should be retained in the Registry. I don't think Norton would prevent that being saved but it might be worth your while to check exactly what "blocks" it puts in place, perhaps even asking Norton Support if their software can or does block such data being written.
If that is not the solution, I think you may need to create a Support Ticket. I doubt very much whether uninstall and reinstall would effect any change to this!