The inbuilt Windows notepad program is okay. It is small, and edits text files without too much complaint. But it is very limiting. There are a lot of things it won’t do and there are many better alternatives.
So an entire new genre of text editor has been created: the notepad replacement. Light, integrated with windows, but much more capable.
Notepad++ is GPL, so it is free to use, and powerful. Simple things like being in colour make a text editor much easier to use, and figure out any typos you may have made. And tabs (like in firefox) that allow you to easily flick between documents — something that really annoyed me in metapad, and was hugely frustrating in regular notepad.
It doesn’t have as nice an icon scheme as Notepad SX, but overall is a much better package. Why don’t you give it a try? (mac and linux users exempt)
Let me know if you have found a better gui text editor than Notepad++ and I’ll give it a try.