Re: Unable to install Nvidia driver
I would suggest changing "vesa" back to "nv" for the time being. Then, as suggested, try booting into single user mode, or if you're not sure how to do that, after booting your computer, when you're sitting at the login screen, press CTRL + ALT + 1. This should put you at a console.
Once there, type "telinit 3" without the quotes, and hit enter. This should put you into the 3rd run level, which nVidia actually likes compiling in more than the 1st run level (single user mode). Hopefully, that should cause X to close for you. Then, try installing your driver.
If it still complains about X already running, you can log in as root (which you should be already) and try typing "killall X" again without the quotes. That might do the trick for you.