|OtheHill is right, unless you have a single drive bay, as in a laptop.|
Make a Windows 7 Repair Disk on that computer unless you already have one.
Swap the drivesa and try to boot it. If it does not, boot to the Repair Disk and do a Start Up Repair. This will fix or create the boot files that might not have been copied over. Once you have it running, launch Disk manager. You will probably find a partition somewhere around the 120GB for your OS partition that was cloned. At this point, you will need to decide of you want one large partition or two. For one large partition, you will expand the current partition to cover the entire available space. For the multiple partition set up (one for your OS and programs, and one for your personal files. For two partitions, just create a new partition for all unallocated space and format it (NTSF). Etc. Files in a separate drive or partition is best.
You have to be a little bit crazy to keep you from going insane.