Reinstall the OS. The amount of time that you or anyone else would spend guessing what you did, is longer than the amount of time it would take to reinstall the OS. If you have licensing issues with reinstalling the OS, then get a different hard drive, reinstall the OS on that, see what the msconfig looks like, and maybe that will jog your memory about what you did to it.
Sometimes there are various restore points or system repairs or corrections you can do, with an installation disk or whatever, that are less than a fullblown clean install and will work. However it's often tricky to figure out which path through the tools will get you what you need. Those Windows startup disks are definitely not designed to be user friendly for system fixing operations. In other words, good luck with that. You're going to need to be patient with trial and error there, same as with trying to tweak your system in the 1st place.
I am pretty sure I just used a Windows 10 installation DVD I got from "somewhere" to do the job. You can figure out where to get one from. My 2 laptops are actually legitimately licensed. They were upgraded from Windows 7, back in the stone ages when MS was offering the Windows 10 upgrade for free. So I don't have "proper" Windows 10 reinstallation media for them, I just have to make do with tools I can find.