If you did a image of the entire old disk this most likely include partition table as well, so the copy of your partition need be resized. There are different ways to do so, like ppl already mentioned either at restore with image software or with apps like Partition Magic, GParted etc
Inside the Disk Management tool (My Computer->Manage->Disk Management) you can see usage of your harddisk, and also rezise in the more recent windows (win7)