Well not literally of course!
When I am doing training to transfer across an OM installation I like to show some of the things it can do. It is better to use the onsite system that has been installed as the server names will be familiar. With MOM 2005 I used to use a virtual machine so I could demo how to do certain things. This was OK as when I finished I switched off the VPC without saving state so it rolled back to how I last saved it.
With 2007 it is heavier on the VPC (needed to buy a new laptop to run it properly!) but as they have changed how management packs work I find the following easier. I create an MP called Delete Me and then I demonstrate how OpsMgr can be used to create simple rules and monitors and such and make sure these all go into the Delete Me MP. When I am finished I can just delete the MP. Much quicker and simpler than firing up a VPC.