For PC’s older than 5 years, there is Xubuntu: http://xubuntu.org/
For newer PC’s there is Ubuntu: http://www.ubuntu.com/
For professional media users, there is Ubuntu Studio: http://ubuntustudio.org/
Your computer will run faster, much faster!
Ubuntu does everything Windows does, and OSX, and yes it installs on Mac hardware too, I know because Im running Ubuntu 14.0.4 on a 27″ iMac. There is a wealth of FREE software too, check it out