Your Ubuntu 12.04 is running in 2D mode. Many features will not be available.(Ubuntu 12.04)

What does that means and how to switch from 2D to 3D. I have a AMD Radeon7670M I tried installing and re installed the driver it recommended in additional drivers and i have checked synaptic package manager all the 2D and 3D related results are marked green.Now What to do i am very confused.

Okay, now I have faced this exact same problem myself and solved this a few days previously. My previous answer was in accordance with the standard procedure for troubles regarding logging in to Unity-3D

Apparently, the official drivers that are tested by Ubuntu are not being detected and are in effect worthless.

Here is the solution I found to the issue (quoting from another site) :

http://nerdysermons.blogspot.in/2011/11/solve-graphic-driver-errors-unity-3d.html

There are 3 suggested methods that are given in this post. I have tried all three and the third was the one that worked for me.(That is the option where you install the open source drivers removing all the existing drivers). The second option actually caused my system to hang after the Ubuntu splash screen.

The procedure given in the above site, for simplicity's sake, and for your ease can be summarised as follows:

1. Prior to taking any of the above approach, run this command to install dependencies :

   sudo apt-get install build-essential cdbs fakeroot dh-make debhelper debconf

2. Install Open source Graphic Drivers (Recommended) The below command will remove all traces of Ubuntu's default fglrx drivers (if installed).

   sudo apt-get remove --purge fglrx fglrx_* fglrx-amdcccle* fglrx-dev*

3. Remove the existing xorg.conf

   sudo rm /etc/X11/xorg.conf

4. Reinstall the xorg.conf

   sudo apt-get install --reinstall xserver-xorg-core libgl1-mesa-glx:i386 libgl1-mesa-dri:i386 libgl1-mesa-glx:amd64 libgl1-mesa-dri:amd64

5. Configure xorg

   sudo dpkg-reconfigure xserver-xorg

6. Reboot the system

   sudo reboot

This worked for me just fine. Hope it works for you too.

Ah, this happened to me, and the solution is easy. First, log off. (Or go to the login screen.)

Now, as shown, click the Ubuntu Logo.

It will open this. Click 'Ubuntu' (Not Ubuntu 2D.) Then sign in as normal. Note: This will always be the default setting. To change it, use these steps again.

Sorry about the formatting. It's quite hard.

Oh, and the options on the 3rd image you might not have.(E.g. GNOME)Unless you installed them.