As Bret Hampton pointed out there’s a lot that we don’t know about your system that could point to a possible solution.
You also have to be aware of your need for older versions (project compatibility, stability, plugin compatibility etc.), but for the most recent older versions these can still be installed via the Creative Cloud app. This is only for the most recent older versions though, nothing as old as CS5/6.
That being said, I recently went through this process. I went full nuclear on Adobe but one step shy of a reformat. You can go through the steps provided by Adobe themselves in using the CCCleaner tool.
In my case, the CCCleaner tool still didn’t clean out everything. I still had to manually delete a lot of folders/files in my %appdata% and %programdata% folders as well as deleting keys within the registry (<i style=”font-weight: bold;”>beware if you go this route as you can irreparably harm your windows install! Be very sure you know what you’re doing if you do this!).
Whatever your choice, best of luck!