Most cloning programs will not do a "direct clone" to a smaller drive
even if the volume being moved will actually fit on the smaller destination drive.
Even a "drive image clone" typically won't work, because part of the data
being saved as part of the image is the volume of the drive it is supposed
to fit on.
when I personally migrated to an SSD, I was doing my migration from a 100gb partition on a 500gb HDD drive to a 120gb SSB.
The way I had to do it was as a "partition clone" just moving the 80-odd GB on the 100gb partition to the new drive.
There was a "rub" with that however... what resulted was not directly bootable
because the 100mb system reserved partition that is typically part of a windows7 installation was NOT cloned with it.
However partitioning and formatting a HDD as a separate operation before a windows installation and installing windows as a second separate operation
blocks the creation of that 100mb system reserved partition (this partition is created "integral" with the system partition itself)
So the work-around of migrating to a smaller drive was fairly simple once I figured out what was actually happening....
Clone the OS, stripped down as much as possible to another convenient external drive (size irrelevant provided it actually fits on the drive)
Then "mount" that image to the target SSD drive.
This will not be "bootable"... yet
The last step is using an appropriate windows installation disc boot from the installation disc and at the last "page" before the disc installs windows on the drive
choose "Repair Windows".
This creates a new bootldr and "System reserve" inside the operating system partition
After this operation completes you can go into disc management and expand the OS partition to the desired final size (more than 120gb is not necessary for a windows7 installation)
This all sounds more complicated than it actually is, but this basic process allows migrating a windows operating system from any drive size to any other drive size on which it will actually fit.
But you need to use cloning software that will allow you to clone as "partition image" as opposed to "disc image"
I used Clonezilla