Notepad++ - cool and free editor, has syntax highlighht for many languages, its possible to define your own languages. IMHO best replace for M$ notepad.

PolyEdit - simple and easy word processor. Supports rtf and doc formats. A good replacement for M$ Word for a good deal of cases.

NoteTab - Small and nice editor for HTML.

AnyEdit - Nice and free text editor.

VIM - VIM is VIM. Bug it's for those who like it.

WinMerge - Simple (and free) file diff and merge utility.

ISpell - Free spell checker for Windoze.

KDiff3 - nice and free 3-way diff/merge.

Python - very powerful and flexible (and free) scripting language with lot of free libraies. BTW its author now works in Google.

Ruby - very powerful and flexible and free scripting language (combining in itself many features of such languages as Smalltalk, Python and Perl).

Lua - Simple and fast scripting language, easy intgratable into applications. Used in a lot of games -Far Cry and STALKER just to name a few. Free, open source.

Panda ActiveScan - you can check your computer for viruses online.

CureIt - free (and it's updated every day) antivirus utility.

AVG Free Edition - Nice and free antivirus.

Far - really cool 2-panel file manager (like a Norton Commander). I just can't stand that stupid Explorer.

a lot of plugins to Far.

PIL - Python Image Library - Very nice and powerful library to work with images. Nice tool to create new or modify existing texture in a procedural way.

ImageMagick - powerful set of tools for working with images.

FireFox - Cool and free replacement to M$ abomination (IE) - no shit like VBScript and ActiveX, A lot of settings, plugins, skins and extensions. A good deal more secure that M$ IE - pity you cannot just throw IE away from Windoze.

Thunderbird - Cool mail and news client. Fine addition to FireFox.

NSIS - Nullsoft Scriptable Install System - really cool tool for creating installers. Free for any purpose.

Inno Setup - Nice and free (GPL) tool for creating installers.

Artweaver - Nice and powerful (and free) image editor. Supports Lua scripting.

Blender - really powerful and free softare for modelling and rendering. Open sorce, support for every major OS. Suprts Python as a scripting langauge.

Pixia - Free image editor.

MP3Producer - free program to coberting and ripping music. Supports wav/mp3/ogg. Can easily convert your CD to mp3 or ogg. A lot of settigs.

IrfanView - free and a really fast image viewer (and converter). Supports an awful set of image format. After trying it you'll forget (and throw away) ACDSEE.

WinCVS a Windoze client for CVS.

SysInternals - st of useful tools for your Windoze.

RenderMonkey - IDE for GLSL and HLSL.

GLSLValidate - really cool utility to check your GLSL shaders for adherence to standart.