I have a mighty mouse, NOT a magic mouse (a lot of people get them confused so I added a photo) and I can't seem to rotate the screen with the middle button on it. Usually if you hold down the middle button on a regular mouse, and move it around it'll rotate but it's not working. Is there something I can do, like maybe change the settings of the mouse or something?

At first I thought Mighty Mouse was a metaphor.

There's a shortcut key for rotation in case your mouse doesn't have a middle button.
1. You can use < or > button to rotate left or right, but I think it's a bit of a hassle, especially since it can't tilt the camera up or down, and it's only convenient if you use right hand... which is not.
2. There's a similar function to middle button, but I don't recall what. Perhaps it's ctrl+left click, or ctrl+right click. Or maybe it was alt, not ctrl. Try experimenting with it.

I use CTRL up, down, left, right arrows to rotate the camera if my mouse isn't cooperating, it's a little clunkier but still works well.

thanks but I already knew about the keyboard rotation, I prefer using the mouse. Thanks tho.

I am not entirely sure anymore but I think that Apple mice are by default set to change from Finder to Dashboard when holding the mouse button. So you would have to change the settings in your System Settings panel to something else. Might have to be MacOs Standard or something like that, or are there settings for individual applications? Sorry, I really cannot remember as I've been using third party mice for ages.

Get a real mouse for the Sims 3. They're dirt cheap.

I fail to see your point. It is a real mouse, although not a very good one for this purpose.

Are you pushing in the mouse button while pushing in the ball? You can't just press in the ball, you actually have to press the ball in hard enough to make the mouse click to register as a middle-click.

The same switch that clicks for left-click, right-click, also has to click for middle-click.

I had a familiar problem too. My mouse was one of those Made-in-China cheap useless peace of crap mouses, and its middle button wasn't working either. The only solution I found was to get a new good mouse. I really couldn't play Sims without that button.

^ That.