Microsoft Edit is a very simple, text-mode (80x25 usually) file editor, and is the best piece of software ever written by Microsoft. In my experience, it has only crashed once, when I attempted to open a file on a bad hard drive I believe.
The file that does all of the work is
edit.com the same version that has appeared in all versions of Windows back to Windows 95. The previous versions were merely QBASIC running in a text editor mode, and were more buggy and a little more cumbersome to use.
Although it has very few modern features, it supports different colors for the background, foreground, highlighted text, etc, supported simple searching, replacing, and was very easy on my eyes glued to a 19" CRT all through the night. It is also incrediby fast, and very small.
No matter how bad your system is doing, you can be sure that
edit.com will help you through it.