For some reason no matter what I do in regards to getting proper ATI Drivers, nothing works. However, testing out the OS in a Live USB is actually perfect. Full-screen flash works, 3D graphics work, and everything is snappy.

Is there a way I can install Ubuntu without the "default" graphics drivers changing? Like I said, everything is fine and dandy until I actually install the OS and reboot. Then I'm greeted to a glitchy, useless mess, which prompts me to switch to a slower, laggier Proprietary driver. I have an ATI Radeon HD 6850 graphics card, and I'm on Ubuntu 12.04 (x64).I tried going into Etc>X11, but I can't find any Xorg.conf files. There's no way of me ID'ing what the graphics settings are from a Live USB/CD, is there?

TL;DR - When I install Ubuntu, the graphics suck. However, everything works 100% fine when I'm testing it out with a Live USB. I'm certain that something happens to the drivers once I install the OS and reboot. What can I do?