List of recommended Windows software

Video Players

• MPC-HC - open-source; with the madVR renderer for GPU rendering and more features (download here)
• PotPlayer - open-source, supports madVR and H.265 playback. A fork of KMPlayer. (Download here)

Audio Players

• foobar2000 - freeware; lightweight and customizable
• MusicBee - freeware; customizable and powerful
• MediaMonkey - freemium; powerful media player with a great database
• AIMP - Freeware, considered successor to WinAmp

PDF Readers

• SumatraPDF - free and open source document reader

Image Viewer

• IrfanView
• ACDSee Classic
• Picasa Photo Viewer
• Xnview

Image Editor

• GIMP - A popular Photoshop alternative - as good as it tries to be; known to be buggy
• Paint.NET - Started as a MS Paint alternative, now integrates plenty of features such as layers and effects

Video Encoder

H.264&Others

• HandBrake - Very basic
• MeGUI - Supports Hi10P encoding
• StaxRip - Supports fairly advanced audio encoding, batch processing

H.265

• x265 - Pre-alpha x265 builds

Audio Editor

• Audacity

Office Suite

• OpenOffice - If you're an idiot, and want to use a dying and deprecated program [1] for some for some bizarre reason. Oddly, things didn't work out for Oracle, so they gave the license to the Apache Foundation who released it under their own license.
• LibreOffice - After Oracle acquired OpenOffice, it asked community members to GTFO [2]. Since everyone despises Oracle, the developers all jumped ship as well [3] and stared LibreOffice.

Text Editor

• Notepad++
• (g)Vim
• Emacs

Hex Editor

• XVI32
• Frhed

Archiving

• 7-Zip

Encryption

• Truecrypt

Disk Burning

• ImgBurn
• BurnAware - free and non-free version
• CDBurnerXP - free, download the version without botnet (OpenCandy) here

Virtual CD/DVD Drive

• WinCDEmu
• Virtual CloneDrive

Anti-Virus/Malware

• Mircosoft Security Essentials
• MalwareBytes
• Nod32 (non-free)
• Avast - free version available

Firewall

• Windows Default
• Your Router's Firewall
• Tinywall - interesting wrapper for the Windows firewall
• Comodo Firewall
• ZoneAlarm

Defragmenter

• Defraggler

Cleaner

• CCleaner - Clears the bloat left by the apps, from cookies to uninstalleed apps remains
• CCEnhancer - CCleaner additions
• Revo Uninstaller

File Recovery

• Recuva
• TestDisk

Computer Specs

• Speccy
• GPU-Z
• CPU-Z

Virtual Machine

• VMWare (non-free)
• VirtualBox

Virtual Desktop Manager

• VirtuaWin - Allows you to use multiple virtual desktops