A Live CD is an actual Windows Installation that you carry with you on a USB Flash Drive or CD/DVD. The Windows Installation is portable, meaning that you can have your own windows running on any PC you encounter. The Live CDs are most commonly used to repair computers that have crashed or to rescue data from a hard drive before doing a fresh installation. The great thing about a Live CD is that it does not alter anything on the computer you use (almost like a sandbox). You boot the computer as if it is your own (from the CD/DVD or USB). You can pre-install all the software you like, making it available no matter where you are. Sort of a Laptop, but without the hardware.
In the Linux World it has been around for years ( and as Windows XP). But Windows 7, well it’s been a longer road. You have of course been able to download illegal Windows Live Copies on the net for a while – but now at last I am able to show you have to create your own legal copy (for your personal use), provided you own a Windows Setup Disk and license.