Windows is the OS (Operating System)...

Switching all depends on what tasks you do on your computer. If there are specific apps that are only on Windows and they are deal breakers it will be harder to switch.

For most people its my opinion if you really want free (as in speech) OS you will drop Windows. Linux Mint is a good option for beginners and specifically for those coming from Windows.

There is some good advice in the comments already but I say you should try it. Install Mint or some of the others mentioned on a flash drive and try it out. What I hear from people that switch from Windows is how much faster their machine runs with Linux. Its true. Linux will run on almost any hardware. Even really old stuff.