SciTE is a powerful programmer's editor and Notepad replacement based on the popular open-source Scintilla (a component used within many other editing tools).
You don't need to be a developer to use the program. It looks much like Notepad, so at a minimum you can just launch it, type some text and save the file, using all the keyboard shortcuts you know already.
It won't take long to notice small benefits. Pressing Ctrl+N creates a new tab, for instance, allowing multiple documents to be open at once. And Ctrl+F gives you a persistent search area at the bottom of the screen, where you can instantly mark all search hits as well as zip through them one-by-one.
Start exploring the program and you'll quickly discover more. Regular expression searches, find across files, drag and drop editing (select some lines, drag and drop them somewhere else), case conversion, bookmarking, session management.
There's also plenty of developer-oriented power, including syntax highlighting, brace handling, code folding, and options to compile and run programs, turning it more into a basic IDE.
SciTE isn't the most powerful of programmer's editors, but it's also easier to use than many, and the core editor (Scintilla) is one of the best around. If you're not currently happy with some other Notepad replacement, it's a must-try.