I installed non-free drivers just last week via the additional drivers with the system settings. Honestly when I have screw ups like this (I've done this a few times) I just reinstalled Ubuntu (12.04 LTS) and just used my intel cpu. Then last week I tried giving it a try again I just went into system settings then additional drivers then installed the non-free one and then opened steam. Steam gave me an error and I googled it. The results came up with this and it worked and I saved it in Gdrive:
This seem to happen on every 64bits OS. Full bug report here: https://github.com/ValveSoftware/steam-for-linux/issues/321 Solution: sudo gedit /etc/ld.so.conf.d/steam.conf Add next two lines to file: /usr/lib32 /usr/lib/i386-linux-gnu/mesa Then execute: sudo ldconfig Now you should be able to run Steam So yeah I tried that and my gpu worked for the first time in about 6 months so that's how I did it.