Robert Gingras 

You should be able to open your termbases in the latest version of MultiTerm.  
In case it does not work, and the termbases don't get automatically upgraded, you could still export them, then create a new TB in the current version and import the contents. 

I have never upgraded my version of Termium, still working with old technology (why change if it works?). I will have to consider that option if it really is impossible to install it on WIndows 11 (still works on WIndows 10). Be that as it may, I thank you for your reply, much appreciated. I'm sure your solution would work.

Robert Gingras 

I don't think you really mean Termium?  I think that's an online terminology tool related to the Translation Bureau of Canada.  But if you are using MultiTerm 2009 then I would be very surprised if it could be installed successfully on W11.  It's simply too old.

But your termbases will still be usable with the latest version of the software as Walter mentioned.

You are right. Thank you for pointing it out. I wrote Termium, I meant Multiterm. Sorry for the confusion.

I was just wondering if there would be a software patch or something of the kind that would make it possible, but it certainly is easier to get the latest version. Thank you for your input.