Using Microsoft Virtual PC 2007 in XP or Vista
If you have Windows XP or Vista, you can use the free Microsoft Virtual PC 2007 program. If you're already running Windows 7, you can use the new version, titled Windows Virtual PC, as the next section discusses.
To download the 2007 edition, visit the download page and choose the correct version. If you aren't sure of your PC's platform, it's probably 32-bit.
Once it's downloaded, run the setup file and install it.
Then you can use the New Virtual Machine Wizard to set up your virtual computer(s). You'll name your machine, choose the operating system you're going to install, and adjust the amount of memory or RAM you want to give it. Plus you can create a virtual hard drive to your desired size.
After you've created a machine, you can select it from the list and hit Start. The default BIOS will load and look for some type of bootable media. You can use the toolbar menu to use a CD/DVD drive or load a disc image file.
When you're done using the virtual machine, you can either shut it down using the OS or close the Virtual PC window.
Then you close the window, you can choose whether to shut it off (pull the plug) or save the state where you can restore the session later.