With the size of Windows and the many application programs in the hundreds of megabytes now, I don't know of anything other than another hard disk that will hold a complete image for backup purposes. After my system reload, I have 2.5 GBy used on my hard disk.. programs and data.

Of course, with hard disks now just a couple of hundred dollars, a duplicate disk may be the way to go. Protects against everything except physical destruction of your pc.