Where can I get a free operating system to replace windows XP?
Depending on your hardware, you may want to only consider Linux distros that don't use the heavier desktop environments such as KDE, Gnome, MATE, and Cinnamon. Look for LXDE, xfce or Enlightenment instead as they will provide better responsiveness on older hardware.
Or, thinking outside the box, buy a new PC, and Windows 8 will come with it (free / included).
If your computer is still using Windows XP, you'll see a huge increase in speed if you buy a new computer.
I'm hybrid user have used both linux and the windows platforms currently sticking with win8 'cos it's nice but for you I don recommend Linux Mint ( http://www.linuxmint.com/ ) this distribution is based on ubuntu linux which is the most user friendly distribution on the world of linux.
Linux Mint have the same similarities when it comes to the interface what linux mint has done taken ubuntu linux stable and cutting edge distribution and made it more user friendly.
This OS is very stable and when you need any help you can ask in the mint forum as well as in the Ubuntu forum.
You can find a comprehensive list of Linux distributions at http://distrowatch.com/. The vast majority of them are free (and the description will tell you if they're not).
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