Age old problem that must have been solved previously. Can you install or reinstall Windows 7 in a manner so that you do not have to reload all the patches and your apps so the registry shows a “clean/new” setup? I realize Fred has a no-reformat article but that is only part of the issue with an aging OS. By the time you completely patch the OS and reinstall apps and update them it requires almost a day of my time (not all at the computer of course).
Could you make an OS image once you’ve done it all and recover to that at some point later? You might then have to further update that image and save another image. Isn’t there a better way?