You can set up as many virtual machines as you want - your only limit is available disk space, the system requirements of your chosen VM and whether or not you have valid install media (and product key). Parallels enables you to emulate just about any flavour of Windows as well as older builds of OS X and even Linux too. You can even manage it without paying a single penny thanks to VirtualBox, but the truth is, if you're serious about running Windows apps on your Mac, then Parallels Desktop is the tool to choose. These days, running Windows on your Mac is pretty straightforward thanks to virtualisation software.
