How To Use Windows Virtual PC to Save Your Old Boot Drive

Thanks to new tools from Microsoft in Windows 7, you can preserve your entire hard disk on another drive as a Virtual Hard Disk (VHD).

So don't worry that you'll forget important data on your old drive --just freeze it solid, like Han Solo in a block of carbonite.

Source:
http://www.maximumpc.com/article/howtos/howto_save_your_old_boot_drive_windows_virtual_pc