Windows 7, can't detect graphic card

Hi, I'm new here because I've been searching everywhere and I can't find an answer. Recently, I bought and downloaded The Sims 3 Supernatural, because I'm a huge fan and have all the games. Well, after I played the first time, and shut it off, my screen resolution went really big, so I adjusted that, then I noticed that my computer has been very laggy, and it recently told me it doesn't support 'Aero effects' So, I assumed it was the game, and uninstalled it. Then I re installed it, and now it is telling me that it doesn't have a graphics card to support it. I am not very intelligent when it comes to computers, and I have no idea what to do. I went to the screen to check what graphics card I has, and it says that it is unavailable.