Good free software for Windows

To my knowledge, the applications listed below are licensed for free use by non-commercial, home PC users. I have tried my best to compile a list of good, safe, free software, and I've tried the majority of them, but since I didn't create them, I am unable to guarantee the quality, compatibility, safety, or really anything else about these products.

Improvements to built-in Windows apps:

• Firefox - web browser with useful security features and lots of free add-ons available.
• Paint.NET - drawing and photo editing tool with lots of neat features (may require installation of .NET framework from Microsoft)
• PowerCalc - great calculator with memory, graphing, and history display; for Windows XP only
• Revo Uninstaller - a more thorough way to uninstall applications from your PC
• CDBurnerXP - CD/DVD burning software with lots of features

Staying safe for free

• AVG Anti-Virus Free - decent realtime antivirus scanner; most updates require no user intervention
• ThreatFire Free - supplemental protection to help protect you from viruses and spyware; should work with most other antivirus and antispyware programs
• Sunbelt Personal Firewall (unregistered/free edition) - firewall with enhanced protection over that offered by the built-in Windows XP/Vista firewall
• KeePass - allows you to store all of your passwords in a single, secure database that can only be unlocked with a master password or master disk (just don't forget the master!)
• McAfee SiteAdvisor - tool that alerts you to websites that are known to be dangerous so you can avoid them; not always the most up-to-date, but a decent safeguard
• MailWasher - anti-spam application that helps identify spam and allows you to delete it straight from your internet provider's mail server (i.e., before it ever reaches your PC); not intended for use with webmail accounts like gmail, hotmail, etc.

Free replacements for costly applications

• OpenOffice.org - a complete office suite, similar to Microsoft Office; includes equivalents for Word, Excel, PowerPoint, and Access; can open and save most Microsoft Office document formats
• AbiWord - a small, simple word processor that's great for older PCs when you don't need all the bells and whistles of Microsoft Word
• GIMP - a complete advanced graphics program similar to Adobe PhotoShop
• InkScape - a vector drawing application (similar to Adobe Illustrator) for graphic designers
• pdfcreator - allows you to create PDFs by "printing" any document to a special printer that saves the file as a PDF; has some problems with Windows Vista
• PrimoPDF - another application similar to pdfcreator; better choice for Windows Vista
• KompoZer - a web page editing application that is similar to (if less full-featured than) Microsoft FrontPage and Macromedia Dreamweaver

Free games

• PySolFC - an extensive collection of solitaire and Mahjong varieties
• Enigma - another addictive puzzle game

Other free, useful applications

• Audacity - full-featured sound editor and recorder; great for musicians or others trying to record themselves or remix others' recordings
• Pidgin - an instant messaging program that allows you to connect to AIM, Windows/MSN Messenger, Yahoo! Messenger, and other services simultaneously
• Picasa - a photo editing and cataloging tool that makes it easy to manipulate and organize your PC's photo collection
• Workrave - a program that reminds you to take various types of breaks (you can customize the time intervals) so that you don't get sore from staring at the computer for too long
• StickyPad - virtual Post-It style notes for your desktop

Free web applications

• GMail - a powerful web-based e-mail solution with great spam filtering; takes a little getting used to, especially the way it uses labels instead of folders
• Google Docs - simple word processing, spreadsheets, and presentations that are saved online and can be shared with others
• Zoho Office - similar to Google Docs but perhaps a bit more polished
• Backpack - online to-do list and calendar application
• Remember the Milk - similar concept to Backpack but with a very different feel; try both and decide which one you like better
• Wesabe - a financial application and online community to help you manage your money more effectively
• Mint - another financial application; some find it easier to update their accounts compared to Wesabe; others prefer Wesabe's interface

Free web games

• Orisinal.com - neat site with several small, simple, elegant games that take almost no time to learn (though may take longer to master!)
• WorldOfSolitaire.com - several varieties of solitaire in your web browser
• WordSplay.net - play a version of the classic word game Boggle against dozens of other people
• GamesForTheBrain.com - games to keep different aspects of your mind sharp (memory, visualization, wordplay, etc.)

Free online services

• LogMeIn Free - allows you to access your PC (if it's turned on and connected to the Internet) from almost any other PC
• MozyHome Free - allows you to back up your documents and settings to their server in case your hard drive dies or you accidentally delete a file

Sources for more free software

• SnapFiles Freeware - directory of free applications sorted by category and including user ratings (hints: avoid the ads at the top and side of the screen, and avoid programs that are more than a few years old when possible)
• OpenDisc - another collection of free open source programs designed to be downloaded (long download) and burned to CD
• OpenEducationDisc - a variant on OpenDisc geared more towards educational software