All Unix flavors have the vi (as in VIsual) editor available; and many have the much more usable (and much more expansive) emacs (as in "Editing MACroS"). Early MS-DOS versions came with edlin (if you've ever used edlin, you must see this edlin site!). Since then, all Microsoft operating systems have shipped with the more user-friendly character-based editor, Edit, and all Windows flavors have shipped with the ubiquitous Notepad.
Notepad Problems
Besides leaking memory savagely, Notepad is renowned for some other flaws, including its stupid inability to have more than one file open at a time, and limiting the size of that file to a miniscule number of kilobytes.
Replacements
When NT first came out, you had Notepad, and 16-bit editors from earlier versions of Windows. By the time of NT 3.5, there were two more excellent freeware/shareware editors added to the mix which were coded natively for NT: the freeware Programmer's File Editor ("PFE"), and the $30 UltraEdit 32.
Judging from the alphabetized sections of Winfiles.com's NT Text Editors page, you can determine that there are now many, many more editors available for NT. (Note that some of those, however, are not "text editors" at all, in that they have proprietary formats and save things other than plain text, which is a big no-no).
Ultra Edit as My Primary Editor
A first requirement for any Notepad replacement should be speed and small memory footprint, and Ultra Edit is nothing if not that. It's a fast load, in part because no matter what you try to open, it loads only part of the document into memory, using disk-based text editing.
Its speed makes it useful as a file viewer as well. In fact, I find it works faster than Microsoft's Quick View. I keep its shortcut in my Send To folder so I can view files without extensions, un-associated files, or files normally associated with Memory Hogs.
And a particularly good file viewer it makes, since it can automatically detect and convert a Mac or Unix file to DOS (in other words, it can get rid of the gibberish at the end of each line in those text files); reformats paragraphs nicely (for example, changing CR/LFs to word wrap); and automatically opens binary files in HEX view.
