Hello, I was trying to install the driver per the instructions in the first post for this topic and my system is completely screwed up now.

After executing the following step:
sudo tar xvzf z600llpddk-2.0.tgz -C /

My user no longer existed in the sudoers file. My user no longer has any rights to do anything.
I rebooted, but now Xwindows can't even start.

What happened, and how do I recover?