I have just installed Ubuntu 14.04 LTS alongside Windows 7 on Dell Optiplex 9010, all in one system. As I boot from my bootable pendrive then screen flickers. I thought that problem may get solved after installation is complete but after installation screen is still flickering. Far left side has less flickering compared to far right side. Since Everything is working fine in Windows 7 so it seems issue of graphics drivers but I could not find any driver. I tried to install Ubuntu 12.04 LTS but problem was not resolved.