Here is what a friend of mine discovered yesterday.
You cannot restore a Windows Complete Backup to a smaller partition than the backed up partition even if the data can fit well within the new partition.
This is what he was trying to do. He got a new SSD which is 160GB. He wanted to use it as a replacement for his Windows drive which is 320GB. He only had about 80GB of data on it. So he did a complete backup to an external drive and then tried the restore to this new drive. It won’t let him do that because it said the partition was not big enough.
The solution is to shrink the partition on the original drive to equal or smaller size as the new one. Sometimes you may not be able to shrink because there is more data or there are immovable files like page file and hibernation files. Disable these options and reboot the computer to get rid of those files and you should be able to shrink the partition.
In my opinion, the backup should have stored information about how much real space was needed based on the last sector that was used or something like that. The backup could even give an option to defrag and move the files to the beginning of the partition so that the restore wouldn’t need the same size hard drive.