OK, thanks guys. Have to say I am a little bit underwhelmed by the publicity machine. Not your fault, I know, this is a peer forum.
When a menu item says check for updates, I expect it to do what it says on the tin.
If it is not capable of undertaking a major update I might at least expect it to notify me of the availability.
And when I paid for the pro version I provided an email address to receive the registration key. Other software providers are not slow to try to pump upgrades at me when they are available.
Oh well, I have now installed version 5. Finding the sub-page that tells me how to get the licence file is not obvious from links off the home page. For that I had to click on the link in Zyndstoff's signature.
Then I thought how neat it would be to try out the virtualisation. So I disabled sandboxie and tried it out. Seems not quite as flexible as sandboxie and it started hogging resources (100% CPU etc) so I thought I would go back to the old tried and trusted. Only that Avast did something to mess up the sandboxie installation, so I had to reinstal that software.
Anyway, I seem to be back to normal now.