Critical Error, preview doesn't show up, interface not registered

since for a couple of days PDFCreator was giving me issues, I decided to update it to the latest version released, 4.0.4.
The problem is that PDFs are now printed, only that the generated file is no longer previewed, but the following message appears in its place.


Critical Error!
Failed to check launch permissions.
Failed to communicate with Windows service to check "PDF Architect 7 - MDI-APP" application data.
Interfaccia non registrata.
[Interface not registered.]

The exact same message appears when I try to launch PDF Architect (which is installed) from PDFCreator.

[You have already installed PDF Architect on your computer - Launch PDF Architect]

I have already tried to uninstall PDFCreator, reboot, reinstall it and then reboot again, but the issue persists.
What should I do? (I have an old PC with Windows 7 intended for retirement, but as long as it resists I'd like to keep using it!)
I look forward to hearing from you.
Thanks in advance, and best regards,

Today I have installed the latest released version of PDF Creator, 4.1.0, but nothing has changed. I remember that with previous versions I could choose during the installation procedure whether or not to install PDF Architect - and I declined, because I don't need it - while now it's installed by default. If there was a way to selectively uninstall PDF Architect I think I could solve the issue... but how can I do it? Only PDF Creator is listed in Programs and Features.
Please help me: although it's not a serious issue, in the long run it's rather annoying.
Thank you in advance!
Best regards,