WordStar if you want to that route. They still make WordPerfect if you inclined to buy it. Might as well get the keyboard templates they used to sell for WordPerfect and Lotus 1-2-3 while you're at it.
I had the same issue as you and I've settled on cherrytree. It is essentially a way to see and organize all your notes in one place, without having to look all over your folders to find That One Note. And you won't lose anything. The only downside is that the dev is very open about his political views but it's only one icon you can ignore.
Abiword is a good lightweight alternative, or you could source an older version of Microsoft Works. That said, Wordpad is still lightweight text editor, it shouldn't be slow on a modern machine. Might want to check that it's not another issue.