Graphics kernel boot options:

use radeon for amd/ati cards, i915 for intel based motherboards, ,,,  These are the most common examples.

    nvidia.modeset=0
    nouveau.modeset=0
    radeon.modeset=0
    i915.modeset=0 
    r128.modeset=0  (for very old ati rage 128 cards...)
    If you don't know the brand you may use just one word:   nomodeset
    Your will find the full range of drivers and more info at Xorg.org wiki

Press [Ctrl]+[X] to boot with this added parameter. This parameter will not be saved, just used in this single boot and nothing is damaged. To cancel without changes press [Esc].
Hopefully, the system will boot into a default graphical environment and you will be able to install/reinstall driver or configuration packages. In my case I solved my issues in a old nvidia cards (Quadro NVS 280 and geforce 7300LE) using a legacy nvidia 96 or 173 drivers, respectively, in place of nouveau. And nvidia-settings package.