I'm going through the forum now (to get an overview of not only my own posts)
I tried to install both ATI and Nvidia drivers and to configure the X server with ati, nv and nvidia, but every time the system told me "Failed to start the X server....".
I finally tried to set up the X server with vesa and it finally worked well.
You can't have both nvidia and ATI in the same computer (well - you can, but that's another story)
Vesa almost always works but is really crappy and you may have messed up your X....(server - not partner
vesa is always there...
You are a noob, so...
Fire up Envy (from the menu) and uninstall all you can. Then let it install the driver for your card, and it's good at selecting the right driver, but you should at least check that it installs nvidia if you have that and ATI if you have that. If you have another brand it becomes more complicated
This should give you the benefit of good video drivers
You may also have to run
sudo dpkg-reconfigure -phigh xserver-xorg
from a terminal