I just bought my first 5.1 speakers... help me getting true surround

I'm noobie at this stuff, perhaps someone could inform me on some things. I bought a logitech z506 and have it hooked up to my pc via analog 5.1, it's mainly for watching movies (and some games). What do I need to watch movies in true surround dolby/dts? How about when it comes to gaming, do I need anything else for gaming surround?