kraftwerk

If you already have data on the 120 and want to keep it, I'd start by repartitioning the 120 to give room for the stuff to be cloned off the 40. I've used BootItNG from http://www.terabyteunlimited.com/bootitng.html to do a repartioning job "on the fly" for 5-6 years now, without a problem. With BING, you can repartition the free space on the 120, then reshuffle the free space to the front, and have the existing data safe.

After that, use whichever cloning app you like to clone the stufff from the 40 to the 120. Of course, it is always advisable to back up all data, just in case!