How to find out what graphics driver is installed?

Run sudo lshw -c video | grep 'configuration' to see the video driver used, or sudo lshw -c video for more detail. i915, for example, means your video adapter uses the Intel 915 drivers; nouveau means you have the Open Source drivers for NVIDIA.

In the Xubuntu menu click on Settings Manager. This will open the Settings window.

In the Settings window under the Hardware heading, click on the Additional Drivers icon. This will open the Software & Updates window and show the Additional Drivers tab.

If you have a graphics card driver installed, there will be a black dot appearing to the left of it, showing that it is installed. The recommended graphics card driver, if there is one in the list, is the one that has [Recommended] appearing after it. You can install the Recommended driver by selecting the Recommended driver from the list of drivers, clicking the Apply Changes button in the lower right corner of Additional Drivers, and then reboot to enable the graphics card driver.

Click on the Ubuntu icon on the upper left corner.. then search for Additional Drivers.. click that.. wait for it to check.. and see if you have any driver checked on available.. if not .. you gotta "activate" meaning to install one of them.. it's better to stick with stable releases.. ( check the description of each ) Good luck