I'll go ahead and admit I was pretty clueless. I knew that Apache HTTPD was a webserver, and I knew that PHP was a dynamic scripting language. I just wasn't sure to go about installing them. Well after one week of trying to install from the .zip files (which doesn't go well if you don't know what you're doing), I finally discovered the .msi files. .msi files are Microsoft Software Installers. Feeling pretty proud of myself, I launched into installing Collective Access...except nothing happened. Apache was running from what I could tell, but I really had no idea how it worked. As for PHP, I just assumed it was working. I mean, I ran the Microsoft installer, right? WRONG! CollectiveAccess install wouldn't run at least partially because PHP was not actually running. (I tested it by trying to run the PHP info script.)
Incredibly frustrated yesterday, I uninstalled EVERYTHING, and then decided to start from scratch...again. (I'd uninstalled and reinstalled apache hundreds of times already in my mind.) This time when I searched online though, I searched by a specific version of PHP, and I stumbled upon ProgramOften's youtube tutorial for installing PHP 5.5. I watched both the tutorials below, and voila! I now have Apache HTTPD 2.4 and PHP 5.5.19 successfully running on my sandbox. Not only that, but I feel like I actually understand both of them a little better. As a result, I was able to successfully install CollectiveAccess. Thank goodness! Of course, I'm still on the uphill slope of a learning curve, but I'm back to enjoying the experience now that I understand the first steps!