Want to try Linux or Windows Vista on your existing Windows XP computer without doing any installation or a LiveCD ? No problem, you can run all them at the same time "virtually".

Virtual Machine (VM) Software like the popular VMWare Server from EMC or Microsoft Virtual PC 2004 lets multiple operating systems run on the same computer.

For instance, you can create a single Windows XP Virtual Machine and then install beta software like Firefox 2.0 or Windows Vista or even Office 2007 onto the VM without even touching any file of your existing OS.

Software fans, who install any new software release the moment it appears on the company ftp servers, would be delighted to hear that Microsoft has released Virtual PC 2004 for free, a technology they acquired from Connectix Virtual PC.

This announcement comes just months after EMC decide to release their server edition of VMWare for free. Microsoft is also offering the free download of Virtual PC 2007, with support for Windows Vista in 2007.

Windows Vista Enterprise customers will have the right to install four copies of the operating system on a desktop for a single user. The Mac version of Virtual PC won't be available for free however.

Don't confuse a VM with a dual boot software like BootCamp or Parallel Desktop for Mac. Running VM software is just like opening a Word document - you double click on the VM name and it loads in a new window just like Word. You can also start more that one VM like Linux and Windows at the same time. You won't have to reboot.

Download Virtual PC 2004 | Microsoft Software at McDonald prices

VMWare vs Microsoft Virtual PC - Comparison of virtual machines