Textadept

It has multiple split for the main window, where you can put several files.
It allows syntax coloring.

Simple, lightweight. perfect.

Almost as good as Scite

This is a masterpiece.
As configurable as vim and emacs, but with a saner config language and API.
It's tiny, 15mb memory usage.
It's a mystery why this is not better known.

Mostly great:

• Blazing fast
• Low memory usage (in Linux and even in Windows where it uses the non-native GTK).
• Minimalist (without compromising fictionality).
• Configurable to the hilt.
• Portable.

However,

• Documentation is inadequate in certain cases.
• Struggles when it comes to replacing text (even in a single file).

Portable, small, and just works for basic to intermediate editing of whatever on Windows.

I wholeheartedly agree with this assessment:

http://yfl.bahmanm.com/Members/ttmrichter/software-reviews/textadept-review

Something which only a year ago would have seemed impossible has happened: I've found a text editor to replace Vim. Here's why.

After giving Textadept a try, I now wonder what took me so long to discover this gem. Simply put, it is the most customizable, scriptable, and hence powerful free text editor that I have ever used on Windows since Vim, SciTE, and NPP (inefficient web apps like Brackets and Atom don’t count). This is the text editor that made me fall in love with Lua and has slowly started replacing NPP as my favorite code editor in the toolbox.

To scratch the surface of how extendable this program is, I'll give you a few examples:

• If you are unhappy with NPP’s too-subtle flashing icon when a search wraps back to the top, then just add a Lua event handler to display a dialog box when the search wrapping event is triggered.
• If you want to add a new function to alpha-sort selected lines, then define a key binding pointing to a custom Lua function that does just that (it’s like assigning a variable). I suppose you can also create a custom menu item if you wanted to.
• If your preferred theme color is not included, then create one from scratch (or look in the growing community to see if someone has already created it).
• If syntax highlighting for your favorite language is not included, then create a new lexer from scratch (much easier than compiling a new lexer for SciTE).
• If Intellisense-like autocompletion for your favorite language is not included, then create a new API file from scratch.
• If you miss the editing modes in Vim, then it’s trivial to emulate a similar experience by editing the preferences file.

You get the idea – this thing is a beast. What I love about it is that it’s a relatively fast and resource-friendly beast that lets you unzip and go, no installation required.