I am confused by third-party software

I am a newbie, downloaded Banktree3 to my vintage Vista computer (I still use for practice), and it installed two desktop icons, one marked Banktree3 and the other Manager. I used Manager first and it gave me a sample business Northwind. I experimented with this and then created a practice business, then started creating my actual business. All to the good! However when I accessed the website guides for further assistance they bore no relationship to my input screens.
I then made a backup of my work and closed down. After a while I opened up using the desktop icon mark Banktree3 it opened up a completely different screen, resembling the guides but still differing. However this screen would not access my previous work or the sample Northwind.
Investigation of my folders revealed files with the suffix .manager for my previous work using Manager and .dat suffix for Banktree3. Running Banktree3 did not give me the option of accessing files other than .dat files.
I then considered that it could be my Vista system that was causing the problem so I installed the download on my Windows10 computer. This only installed the Banktree3 version so I still could not access the files I had created using Manager.
So I remain confused

Did you download Manager from the official site? Download | Manager It sounds like you did not.

People do build packages off Manager, rebranding it as their own. Many third-party software distribution sites also offer obsolete versions of Manager. I have no idea what Banktree has done, and neither I nor other moderators or users will help you figure it out. Such rebranding is actually a permitted use. But it includes no support. So you are on your own.

The real, up-to-date Manager application can only be downloaded from the link above. And support for it is available only on this forum and at these Guides: https://guides.manager.io/.

Thanks for that. I will investigate my source, it was from a google search. Thanks again.

The simplest way to solve this problem would be to get rid of Banktree completely and download directly from the Manager website.

This way you are assured of the following:

You are using the original program
You have the latest version
You have the support of the forum here which is really good (Thanks @Tut)
The guides in the program match the actual program
it would also ensure that you are using one program instead of two thus preventing this exact kind of problem from occuring.

Have done so, cleared both computers, downloaded again and everything is as I had wished and hoped for. Exactly what I wanted. Thanks a lot.