Virtual machine is no longer news to us (IT Professionals). Virtualized servers have been used on production for years. MS has also launched similar product called Virtual Server and they also changed the licensing to reduce the cost of OS if they are being used on virtualized environment.
The idea is haven't more then one OS running on a computer at once. It is difference from the traditional dual boot mode where, dual boot only allow one OS boot up at once. With the help of VM technologies, one can load as many OS on your computer as you like, provided that your system have enough resource for the guest OS.
For instance, this website, lowtechplace.com, this blog, the gallery and the email are all host by a Linux server (Redhat) running as a guest OS on top of a Windows XP Pro workstation without anything connected to it. Opps, my mistake, new Canon MF3110 multifunction printer connected to it since yesterday. 😛 But there are no keyboard, no mouse and no monitor, oh of course, a network cable is connected.
With the use of the VMWare technology I can basically run multiple instances of the servers for testing and development purpose, on a computer. The cost? Extra disk space and RAM. There are really some other advantages about using a VM. For example, I can simply copy the VM image and run the same instance of the VM at another computer without any problem. As you can imagine, the virtualized environment will not change.
So here you go. You can visit the websites and try it out.