Sorry, but the easiest way is going to be to complete a clean install onto the SSD.
First thing you will want to do is purchase 2 USB drives; one 8GB drive (or larger) for a clean Windows ISO using the
Windows Media Creation Tool and the second, large enough for backing up your data.
Next, you will want to backup your data (documents, videos, music, favorites, e-mail , etc...) to your backup USB drive. You could/should also download the latest drivers for your motherboard/GPU onto this drive, so you have them available once the Windows install is completed.
Then you will want to format your 1TB drive to clean it completely. Once that is completed, shut down your system and disconnect the 1TB HDD. This prevents the Windows install from installing any files onto the HDD.
You will then want to start a clean install of Windows. During the install process, Windows will ask you where you want to install the OS. Go into the Advanced options and you should just see your 120GB SSD. Select this drive, format it, and install Windows onto it. Once the install is completed, use the backup USB (where you stored your previously downloaded drivers) to install the latest drivers for your system.
Now you can shut down your system and reconnect the 1TB HDD and reboot. Once reconnected, you may want to consider moving your default download location to the HDD.
-Wolf sends