first of all download from NVIDIA your driver and it should be put on the folder Downloads in your system
1. open terminal and write su and your pass
2. service prefdm stop
3.press ctl+alt+F5 and in the black screen login (mine root and pass press enter and write su and pass)
4.type cd Downloads press enter
5. type sh (name of your NVIDIA file).run
Background: I bought an NVIDIA graphics card and tried to install its driver. Somewhere along the way I messed up and now I'm running my computer on Cinnamon backup mode (I have Ubuntu but I removed Unity and replaced it with Cinnamon). I want to start back from scratch (prior to this, I was using a core i3 and no graphics card).
I have a NVIDIA GeForce GTX 560 graphic card with Ubuntu 13.04 running kernel 3.8.0-19 (tried with 3.10.0-999, same issue) and whenever i tried to install NVIDIA driver, either by downloading the *.run file from http://www.nvidia.com and installing it as root (during installation it give some errors as it failed to set runlevel), or doing those following steps: