How reinstall the default graphics drivers?

When I installed ubuntu 11.10, 64 bits I didn't have to install any kind of graphics drivers and all 3d efects were working fine. Now, it seems to be that graphics drivers are uninstalled. I can't use unity 3d or any compiz effects.

I have a laptop Sony Vaio VGN-NW330F, my graphics drivers are intel mobile 4 series chipset integrated graphic controller.

The solution is here: http://board.blackbuntu.com/printthread.php?tid=31

sudo apt-get purge nvidia-*
sudo apt-get install --reinstall xserver-xorg-video-intel libgl1-mesa-glx libgl1-mesa-dri xserver-xorg-core
sudo dpkg-reconfigure xserver-xorg
sudo update-alternatives --remove gl_conf /usr/lib/nvidia-current/ld.so.conf

After that I did unity --reset and all is working fine again. Thanks to Micro :)

in general you can run lshw -c video from a terminal to get all the basic info about your VGA, without knowing anything you can also run lspci -n and paste the output at this page http://kmuto.jp/debian/hcl/ to get the name of the required module under a general Debian-like distribution like Ubuntu.

Keep in mind that some modules require additional configuration but usually Ubuntu automate all the tasks for you, but it's always a good thing to google a bit more about the module you are about to install under your system.

Also check di utility "additional driver" in your control panel for further tips.

PS for the same hardware several modules can be available, the site that i suggest usually display the one that are already available in the official repository, for example for an ATI VGA the site display the module radeon but you can also use the proprietary driver that you can download from the AMD website.