Microsoft offers a free application to host virtual machines. It’s a very simple interface and allows a lot of flexibility. After a quick download and quick install, you can fire up a “machine” and install either a Windows machine to test or a Linux live CD by just mounting an ISO file. You should be able to install any PC configuration with this and come up with a great test machine where you’re not going to hose your actual physical machine. With Virtual PC 2007, you can have a sandbox to access really quickly and conveniently. From what I’ve experienced, it’s been more stable than VM-Ware and is free at its full capacity.
http://www.microsoft.com/windows/products/winfamily/virtualpc/default.mspx