Hello Joya D if for example you installed the 2015 Student version and had your full license version 20xx (any other year but 2015) then yes you could have both on the machine. Hope this is an option for you, otherwise no they can't both be installed at the same time because they both use the same path to install themselves onto (which shouldn't be modified from the default location set during install as there's hidden files that automatically go to specific locations in the Windows Registry, if you change it, uninstalling will be difficult and probably a manual process).