There seem to be a lot of posters on this topic, which is already marked as solved. If you are having a similar problem but the solution marked in this thread does not work for you, please start your own thread so that we can locate and assist you.
General information that may help some people:
When you install the base game, if it asks you where to install, usually the default suggestion will be Applications on your Mac's hard drive. If this does not appear, simply navigate to it and then install. If your Mac has more than one hard drive, choose the one that you wish to install your games to. Before doing anything, make sure there is enough space for the game on the drive you have chosen. In the past I have seen players using external drives but they tended to be more likely to have problems so use the normal hard drive if possible.
Once the base game is installed, it is recommended that you patch it up to date. If you find that the updates via the Launcher don't work, use the manual superpatch instead. If you are not sure how to do this, start a thread and ask for help and we will give you more detailed guidance.
If you now decide to add an expansion pack, the procedure is the same - just point the installer towards the hard drive where you installed the base game. You need the base game installed before you can install any expansion or stuff packs.
