Parallels Workstation is a desktop virtualization software for running multiple operating system on a single PC. The advantage of using desktop virtualization software for running multiple OS is it allows you to run Guest OSes as programs on the primary OS, so you don’t have to reboot or fear of messing boot records.
There are several desktop virtualization softwares like Virtualbox, XEN, VMWare and Virtual PC. Parallels offers some neat features for running other OS, it works with both Windows & Linux.
It usually sells for $49.99, but using this Lunarpages offer you can get the activation key for free. Register with your email ID, activation key will be sent to you via Email. Download the application and install, while installing skip the registration step and enter the activation key you received via email. More on Parallels Workstation can be found here. Thanks Amit