Board Thread:Off Topic/@comment-96.43.35.65-20140111175627/@comment-6881629-20150906205545

On your Steam library page for Skyrim (in detailed view) under the achivements theres a section for dlc that will tell you what dlc is owned and installed, also the Skyrim launcher itself shows what dlc you have installed and activated in the data files section. The PS3 has a similar section towards the bottom of the main menu (but it's just a list).

You can tell in-game if Hearthfire is activated buy checking the general merchants they should have some of the new building materials or childrens items for sale, you don't have to get the letter just go ask the Jarl.

Dawnguard should activate at level ten vampires will attack towns and guards will mention the Dawnguard reforming.

Dragonborn will activate after the main quest The Horn of Jurgen Windcaller and Cultists will seek you out.