Although Windows is not a free operating system, it has become a standard simply because it comes pre-installed with most new computers. In the past, this meant you also had to get matching commercial software, which often came at a hefty price tag. Fortunately, the open source movement and the Internet changed the game.
Today there are many free open source software options, and  cross-platform alternatives that are less costly than propriety software. In this article we have summarized the most important free open source alternatives to standard commercial Windows programs.
1.) LibreOffice replaces Microsoft Office
LibreOffice was founded by former developers of OpenOffice.org over concerns that Oracle would turn it into a commercial product. In April 2011, however, Oracle announced that it would discontinue commercial development of OpenOffice.org and make it a purely community-based project [Wikipedia]. Nevertheless, LibreOffice has become an alternative for both OpenOffice.org and Microsoft Office.
Like its commercial counterpart, LibreOffice comes with a word processor (Writer), a spreadsheet program (Calc), a presentation tool (Impress), a databases manager (Base), and a lot more. It is fully compatible with standard Microsoft Office file formats but users must remember to save or export their files in the respective format.
Mozilla Thunderbird replaces Windows Live Mail
Mozilla’s Thunderbird is an easy to set up desktop mail client that supports extensions and hence can do many tricks that Windows Live Mail still needs to learn. Unfortunately, it still isn’t an alternative for anyone who depends on syncing (Outlook) contact data from or to mobile devices. (Some have mentioned Zimbra Desktop as a true alternative this app however is not completely open source and we will be covering it in-depth shortly..)
Inkscape replaces CorelDraw & Adobe Illustrator
Inkscape is a vector graphics editor that uses the W3C standard Scalable Vector Graphics (SVG) file format, supporting many advanced SVG features, including markers, clones, and alpha blending. It is rather intuitive to use, which makes it a great tool for beginners.
Another free open source alternative for CorelDraw is Draw from the LibreOffice package
GIMPÂ replaces Adobe Photoshop
GIMP, an acronym for GNU Image Manipulation Program, is a cross platform graphics editor, which can serve as a simple paint program, but also supports advanced features, such as photo retouching, batch processing, or image format conversion.
Blender replaces 3ds Max
Blender is a cross-platform 3D content creation suite that supports modelling animation, rendering, a game engine, and much more. The Blender homepage features a thorough collection of tutorials and a list of movies that were created with the program.
BRL-CADÂ replaces AutoCAD
BRL-CAD is a cross-platform open source modeling software that supports interactive geometry editing, high-performance ray-tracing for rendering and geometric analysis, image and system processing tools, and more. The program has been developed for an impressive 20+ years.
Another alternative to AutoCAD is LibreCAD.
7-Zip replaces WinZip or WinRAR
7-Zip is a file compression/decompression tool that supports many archive formats and also comes bundled with a lightweight file manager.
A full list of free and open source software can be found on Wikipedia.
We would like to know what was the last program you paid for and why?