Download these:
1. VMware Player
2. ESXi
VMware Player is for having a virtual machine (VM) on your desktop (the host). Pretty much, you slice off some CPU cores & RAM for the virtual machine, so if you have a quad-core CPU with 2 gigs of RAM, you could give your virtual machine 2 cores & 2 gigs of RAM, then you assign it some hard drive space, which it keeps in a file (default is a growing file, so if you make a 60gb virtual hard drive, it's only as big as what is actually installed rather than being a full 60gb size right off the bat).
You can run as many virtual machines as your machine allows. At work, I use a few different virtual machines on my host (Win7). One is a work VM with all of my work stuff like Exchange & whatnot, one is for a dummy domain user for testing network changes, and one is a throwaway that I use for checking virus files or testing new software. I keep my VM's on a separate small SSD drive (you can get a 240gb for $99 these days, if you really want to get into it), which is handy for running them fast because then you're not doing your host OS read/write on the same drive as your VM virtual drive read/write, which can clog things up if you're doing a lot of booting & file saving or reading in your virtual machine.
ESXi is pretty cool if you have a spare 64-bit computer lying around. Rather than using Windows as your host, you install ESXi as the OS on the computer & run it headless (like a server, no monitor or anything), then remotely connect to your server via Remote Desktop. Computer requirements are listed on page 13 here:
https://pubs.vmware.com/vsphere-55/...center-server-55-installation-setup-guide.pdf
This is fun to do because you can virtualize all kinds of stuff - a Windows machine for doing downloads, a media server for streaming videos, a security camera server, a firewall like pfSense or Untangle, a DIY domain setup using Zentyal, the list is endless. Really fun to tinker with, without having to physically setup yet another computer just to play around with a particular OS.