Most of the world's personal computers run Windows, but Windows isn't the only operating system around. Right now, you're probably thinking of Apple's OS X, and mobile operating systems like Android and iOS.
However, there's another operating system you might want to know about. It's called Linux and it's been around for a long time. In fact, it runs a large chunk of the world's servers and embedded computers. Android is based on it, and OS X is based on an offshoot of Linux's predecessor. So, what does that have to do with you?
A few good things about Linux are that it's free, most of the software for it is free, and it's very secure. There are also dozens of versions around targeted toward certain audiences. Linux Mint is one we've talked about before that's a good Windows replacement.
However, Linux Mint still has a learning curve for new users, and the default version requires newer hardware to run well. For older hardware, or a more streamlined experience, you might try a Linux version called elementary OS.
Elementary OS is visually more similar to OS X than Windows, but it's simple enough for anyone to use. It's also very lightweight, which means it runs great on older hardware, even low-end hardware from the mid-2000s.
You can try elementary OS before completely replacing Windows or OS X by creating a bootable USB drive using a program like Rufus. You can check out elementary OS' step-by-step installation guide for more.
When you go to download elementary OS, it will ask for you to purchase the program. It's a community project, so making a donation helps the developers.
However, if you aren't sure yet if you're going to use it, simply enter a Custom amount of $0 and the button will change from "Purchase elementary OS" to "Download elementary OS." Click the button to get started.