You can backup all your data, pics etc. and your game and program installers, but you will have to reintsall all your games and programs.
But you will be installing to a new ssd so you won`t be affecting your data on the hard drives. ( yet )
Put as much data as you can on the hard drive that DOESN'T have windows installed on it, just copy and paste it or drag and drop it.
Do you have a windows 7 activation key somewhere on your desktop pc ?
If you can, post a pic of disk management.
start>right click computer>manage>wait a few seconds>disk management