I replaced Windows Notepad with TED Notepad 5.0
This is truly a worthwhile feature-rich replacement.
Even during installation you get to chooose if this should be a notepad replacement or a standalone program. I chose to replace notepad. Windows cried about the original OS file being replaced. Sob! Sob! Sob! All it takes is a confirmation that you prefer the new executable.
The coolest thing is that this permits you to select text columnwise too! A real handy program.
Its also on Wikipedia, here!