Today, open source software are alternatives to a lot of proprietary software. They are not only available for Unix-like operating system, but lately there has been lot of development which makes it available for the proprietary operating system--Windows and Mac.
 
If you are a Windows user, then even after having bought a licensed version of Windows Vista/7, you will still have to pay for application software--one such example could be license fee for Microsoft Office Suite.

Otherwise, your must be running the trial version which comes bundled in many cases when you purchase a laptop, or you are running a (cracked) version of Microsoft Office Suite ;-).
 
Well, today when we talk about Office Suite, we have many alternatives which can keep us away from installing expensive or cracked version of software on our laptops, netbook, etc.

One such word processing tool is OpenOffice.org. It is one of the best open source software suite for word processing, spreadsheets, presentations, databases and more.

It comes in multiple languages and supports all international open standard format; unlike Microsoft OfficeSuite, which has its own standards like *.docx, *.pptx, and more. The latest version of OpenOffice.org provides support for these proprietary files too.

OpenOffice.org 3 is released under LGPL terms and OpenOffice.org office suite can be used by anyone at any place--government, education, business, IT businesses, or anyone without paying a single rupee license fee. For more information on OpenOffice.org, I suggest, read through this website http://why.openoffice.org/
 
Other than OpenOffice.org, there are quite a few other office suite available for free--KOffice, Siag Office, Gnome Office (consisting of AbiWord, Gnumeric, and many more), etc. If you want your data to be available anytime, anyplace, then Google Docs is an web-based office tool.

P.S.: OpenOffice.org is "free" whereas Microsoft Office Professional 2010 is available for $499.99. The choice is yours!