GMA 3100 is the integrated graphics found on G31 chipset motherboards, so that checks out unfortunately. The drivers look good also, with the Intel drivers correctly loaded and being used.
You might try the xorg-edgers PPA, which would install the newest of the new video drivers and perhaps those will manage to squeeze some extra performance or features from your card. But I wouldn't recommend doing so unless you are happy to do a reinstall if all goes wrong with this. Read the recommendations on trying this from the live session of the installation DVD / USB stick: https://launchpad.net/~xorg-edgers/+archive/ppa