I am new to Ubuntu and have just installed 16.04 on my old XPS15. I tried to select the latest graphic driver for nvidia. Version 361.42 (proprietary, tested) and it wouldn't boot back into the GUI, so I drastically reinstalled ubuntu and now wanting to get it right a second time. I have looked at a large number of different posts on this forum with all kinds of work arounds but I am reluctant to try without making the situation worse. Could it be a matter of just chosing a more recent driver from NVIDIA site or could I select an older driver from the list to get it working? I have attached an image of the available drivers to choose from.Additional drivers list
I found a pretty solid article on Ubuntu forums that seems to solve your issue here: How to get Nvidia 420M working
Apologies for posting an answer that may not be fully correct. I would have posted a comment but my rep is not high enough yet.