if its an old Notebook just keep it clean, more memory will help but an old'ish CPU that will soon start to hit 100% if its full of crap.
Ive got an old Sammy Atom CPU with 2GB Ram (Max it will allow) running Win10 Pro, which I use as a little run around on the go, fully backed up, so not that fussed if I lose it or it it goes bang, but it still runs sweet because its kept clean.
Ive emptied the Start Up on it, the only thing I have running on Start Up is my AV (in my case Win Defender), anything else I can wait or start it when needed, makes a big difference on an old machine.
As TB says, fresh install is the way to go every time, I probably do mine every year or two, especially after a major update, the amount of crap left behind or built up over the years can really make a difference.
Im a great Partition lover as well, Disk Partitions are useful tools, All my Own Data plus the Windows stuff, Docs, Downloads, Vids, Pics etc are kept on another Partition, so my C drive is purely Windows stuff, so much easier to back up or disk clone. and recover if need be.
If youve just rebuilt it, now a good opportunity to clone the drive and kept it tucked away somewhere, I tend to go over board, I clone or disk image the bare Win virgin install Drive, then clone again after my required basic Apps have been installed, ie Office etc, they get labeled and kept for a rainy day.
Weekly within House Keeping I use CCleaner and Glary Utilities to clean then reboot and do a Restore Point, Monthly I also MawlwareBytes and a full Partition(s) Back Up.
Ive probably got a Glary Utilities Pro Lifetime Licence kicking around somewhere, your welcome to have a copy of that if you want to start using it, but again just remember to rid of all these cleaners and stuff from the Start Up Menu.