The fact that Windows 7 is proprietary means that Microsoft asserts legal control over its users through a combination of copyrights, contracts, and patents. Microsoft uses this power to abuse computer users. At windows7sins.org, the Free Software Foundation lists seven examples of abuse committed by Microsoft.
Free software operating systems like GNU/Linux can do the same jobs as Windows, but they encourage users to share, modify, and study the software as much as they want. This makes using a free software operating system the best way for users to escape Microsoft and avoid becoming victims of these seven sins. Software and computers will always have problems, but by using free software, users and their communities are empowered to fix problems for themselves and each other.
You can get more information about each of the sins and how to escape them at windows7sins.org. Please sign up there for campaign news and action alerts to help raise awareness about Microsoft's abuses, the problems with Windows 7, and the importance of free software!