I am a Mac user- however I'll say that the majority of PC users have a Microsoft Surface Pro 3 (or newer model) or a Lenovo Yoga. There are a few Acer and Dell's around as well. There's maybe 2 people with an Alienware computer - which they probably use for gaming in their rare spare time. Really any new PC you buy should exceed the specs list. The testing software supports Windows 7, 8 and 10. I would recommend at least having Windows 10 already installed so you don't have to deal with those upgrade issues down the line. I would also recommend a computer with a stylus as that's the feature that most PC users love in class.
For Mac users on this thread...to address what bon22 mentioned, the class is split about 50/50 with PC and Mac. The Macs are either MacBook Air's or Pro's with a few new tiny MacBooks floating around (the thin pretty ones). The testing software supports OS X 10.7 and up. Meaning, Lion, Mountain Lion, Mavericks, Yosemite, and El Capitan. I would recommend at least the 13" screen because the testing software can get kind of cramped during an exam. That being said, I've seen people using the new tiny MacBook's without issue. The only compatibility issues you may experience are: wirelessly printing to the library printers. Honestly, no one uses this feature (Mac or PC users). We all log into the print stations in the library. The second issue is with the SP (standardized patient) software. It doesn't work on Mac and it rarely works on PC. Again, most everyone uses the school computers in the library, ~20 minutes once a month, to access this software and write a self reflection. Even then, the computers in the library may have problems too. It's just that the SP software is very finicky. Don't let that stop you from using Mac if that's your preference. Years of classes before you have been successful with Mac.
Hope this helps.