Welp.
This is all easier if you have experience with linux or have installed gentoo/arch before.
Essentially, you will be booting from a live cd and making grub boot from text mode.
Get a live ubuntu (or any other distribution's) cd and boot into it.
Open their file manager and find your system (usually found in /media)
Mount the live cd'd /etc /proc and /sys into the /media system boot.
Get in the command-line.
Now, you're going to use an editor of choice (nano, vim, gedit) to edit /etc/default/grub
.
Make sure you use sudo.
You're going to want to find:
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
And change quiet splash
to text
.
Save the file and do sudo update-grub
.
_
Next time you boot into linux, you will have a commandline.
I assume your problem has to do with drivers not working and deniying X the ability to start.
Try removing all of those drivers and reinstalling them.
(I recommed you try the open source drivers since they are way less likely to fail you)
Hope that helped you. :)