I am afraid windows 7 backup can't let you extract of individual files from that whole-drive image. And event it maybe hard if you wish to restore image to free partition drive. If windows 7 think the destination you choose the not the perfect one it thinks. windows 7 backup and restore might refuse to do this.
Try a windows free backup and restore software: support full backup. You can run backup jobs by right click what you wish to include in this backup without running this program. You can even choose to restore part of or whole files of a image file under Windows explorer. I think this is the best you should own. thy easeus backup product. its free edition is of power.