I'd highly recommend Centos.
That is a true or pure linux system, rather than one butchered to make it seem more like Windows.
It's based on the same source code as the commercial RedHat distribution and everything in it is tested for ultimate reliability.
It will run on just about any old PC you can find; one that will barely run Windows will run linux fine.
As it's intended as a business system, it does not have multimedia support pre-installed - but everything is available and it only takes a few minutes to add in:
https://wiki.centos.org/TipsAndTricks/MultimediaOnCentOS7
You can also add the Steam game system, which will allow you to use any games you have previously bought/registered via Steam:
http://negativo17.org/steam-for-centos-rhel-7/
Obviously you do need gaming-grade PC hardware to run any recent games..
(Not all games are available on Linux yet, but SteamOS itself is linux-based so the difference in availability is rapidly shrinking).
Get centos here:
https://www.centos.org/download/