I previously had ubuntu 10.10 installed and upgraded to 11.04. However, desktop is same 10.10 (gnome) as despite the upgrade. How can I disable the Gnome and activate Unity instead?
Unity is a plugin for Compiz Fusion. It works well with Gnome, actually I don't think it works with anything rather than Gnome (someone might want to follow up on this).
To enable Unity, you have to enable the plugin in your Compiz settings. I'd suggest an app called CCSM (CompizConfig Settings Manager) -- a visual interface to Compiz settings. You can get it from the Software Center. Find Unity in the list and enable the plugin.
Update: What if the plugin is already enabled?
Okay what I'm gonna suggest is dangerous, but worked for me. Remember the command
ccsm, you might have to use that from the terminal to launch the manager again. Create a shortcut to your gnome terminal on your desktop (
gnome-terminal). Go to the Compiz settings, go to Preferences and reset everything to defaults.
You might experience some display problems at this point, if your desktop gets unresponsive press
Ctrl+Alt+1, login and type
sudo service gdm restart, you might end up with a bare desktop without a single menu (I did). Run the terminal, run
ccsm and enable the Unity plugin, it'll ask you about some conflicts, ask Compiz to resolve them and disable all plugins conflicting with Unity.
Worked for me at least. Let me know how it goes ;) and good luck!
If you are not seeing any available drivers, check your software sources and make sure that the main, universe, multiverse and restricted repos are enabled.
Then, if you are comfortable in the terminal:
sudo apt-get install nvidia-current nvidia-settings
If you are more comfortable with synaptic/software center, you can open either one and search for the nvidia drivers, then install them (the packages name are nvidia-current and nvidia-settings).