If you have created a backup of "C" drive (an "image" file) restoring that image to a new hard drive will put the contents of your old "C" drive into the entire new drive, unless you have created partitions and can select the one to restore into. An image file of "C" drive won't recreate the old drive's partition structure in the new drive. You would either have to backup the contents of each partition separately and restore into a similar partition structure in the new drive or, the simpler solution would be to install the new drive as a slave drive and "clone" your existing drive into it. That will retain the complete partition structure. Then install the new drive as Primary Master to boot from it. You would need Partition Magic to resize the partitions having cloned a 40GB drive into 120GB, which should leave 80GB as "unallocated" space on the drive.