Tad hears he can run Windows on an Apple computer. Leo says he can, and there's two ways to do this. One is to use Apple's BootCamp. Installing under BootCamp would allow Tad to choose which OS to run when he boots the computer. The other option is running Windows in virtualization. If Tad has a dedicated program that he needs to run on Windows, he can run Windows virtually through Virtual Box, which is free from Oracle. He could also use VMWare's Fusion or Parallels.
If Tad needs Windows to run the fastest, he should use the BootCamp option. If he needs the convenience of running both operating systems side by side, virtualization is ideal. But remember, either way, he'll need to buy a copy of Windows. He shouldn't assume he can get a great deal on eBay, either. Chances are, he'd end up with a serial number that's already been used and Microsoft will block it if he tries to use it. So he should go to a reputable place like Amazon.