At my work I had to make a cluster of machines to setup Voip Solution. For that we needed at least two Linux machines to install Asterisk (http://www.trixbox.org/) on it and then play around with it.
One solution to do that is installing physical machines and then installing the VoIP servers on it, but there was a simpler way and maan! Its kool.
Microsoft Virtual PC 2007 (Free from Microsoft Waaaaow!)
Also free one - VMWARE - The future of Virtualization -www.vmware.com-
Thanks to VMware I have been able to set-up testing lab in on my 12’’ laptop! Awesome! Rite now I am running a Debian and a Fedora working perfectly with different IPs, No need to format to Linux file systems, No GRUB Boot loader or anything. Unbelievable!
At first I thought …. OK, maybe it can do this but with a substantial loss in performance and reliability. How wrong was I!
VMware have a lot of options but MS one is Simpler, both are free though.