First, when you boot, boot into the recovery mode.
You should be in a command line interface now, then enter this code
- Code: Select all
sudo dpkg-reconfigure xserver-xorg
that will restore x to the default settings.
Now to install the drivers for your ATI card, and this is going to be a little more involved. Since neither Envy, nor the restricted driver manager worked for you, you have to install them manually. I have written a guide on installing ATI drivers here
You can ignore the beginning part, as you already have Mint installed, and just go to the part for after installation. Hope this helps.