I have been using Quicken 6.5 forever, and have never upgraded beyond there because (a) it did everything I wanted and needed, and (b) getting to 6.5 removed a function I used frequently, so didn't want to lose more.
Currently I am running 6.5 on a new Windows 11 desktop, and it all works fine, except for the annoying registration prompt (now down to 12 starts, I think).
I note mention of this: "Press and hold and keep holding both the left CTRL and Shift keys while you click Tools and then One Step Update. When the message “You will no longer be prompted for registration” appears, click OK." except I don't have any menu item labelled "Tools".
There are also posts which say simply click "Cancel" every time. Does that really work? It would be annoying, but that would be a small price to provide access to my quicken data file.