If talk of the alternatives being Linux and UNIX is leaving you on edge, consider ReactOS as your Windows alternative.
Originally launched in 1996 as a Windows 95 clone project, the official website states that "the ultimate goal of ReactOS is to allow you to remove Windows and install ReactOS without the end user noticing the change."
In short, the aim is that you should be able to continue using your PC as you did before. ReactOS features over 9 million lines of code and is open source.
However, ReactOS has been in the alpha stage for quite some time now. While some apps, such as Adobe Reader, will run on ReactOS, many won't. It's lightweight, though, requiring just 500MB of hard disk space and 96MB of RAM to run.
One day, ReactOS might be a perfect, free alternative to Windows, but until then, it is available for your evaluation. Install it from the boot CD or run the LiveCD on your existing operating system.
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