Trying to switch from IIS to MAMP; can't view PHP sites with localhost.

Several months ago, I created a php site for myself and got it working locally with IIS. I have 2 more sites in progress, and I've run into the issue of making them work on localhost.

The thing is, I set up the first site back in November, and I have no idea how I got it working. I tried using Apache, then XAMPP, then WAMP, and finally got it working with IIS - that's all I remember. I watched the treehouse video on setting up a local environment using MAMP, which seems much simpler than everything I tried last year. So, the plan is to switch over and start using that instead. I can get MAMP working if I open IIS and hit "stop" under the Manager Server settings, but after doing so, I get the browser error message "localhost refused to connect". I looked for a way to view multiple PHP sites with IIS, but that doesn't work, either.

Do I need to completely uninstall IIS? Is that the only way my computer will switch over to MAMP? Also, php.net says that PHP version 5 and up have a built-in server. If that's true, do I really need MAMP, then?

I swear, I've spent more time trying to look at my sites than I have coding them.

Edit: I checked the first site I created this morning, and it turns out that one isn't working, either. I'm just going to stop both MAMP and IIS and start over.