Backup is good!
Doing a backup for an OS is either complicated (Windows) or useless (Linux). Sometime, it's good to keep a Windows image of your system that is fully working so if anything goes wrong, you can go back to a previous version. The best and free option out there is Linux with ntfsprogs.
Simply boot with Ubuntu livecd and then install ntfsprogs :
$ sudo apt-get install ntfsprogs
Taking an image (where /dev/sda1 is your windows drive):
# ntfsclone --output - --save-image /dev/sda1 | bzip2 > windows-sda1.bz2
Writing an image:
# cat windows-sda1.bz2 | bunzip2 | ntfsclone --overwrite /dev/sda1 -restore-image -
Voila, you get your cloning system. And while the system is cloning, you can surf the web and do your work. Much better than any other "commercial" image system to my opinion.