LE 7.0 uses the older nVidia 304.xx driver whereas LE 8.0 moved up to the 340.xx driver. This change effectively drops support for GeForce 7xxx cards (8xxx is the minimum supported) hence the correct/expected message about your GPU not being supported.
You have three options:
a) Get a newer card (one with VDPAU or VAAPI support would be better).
b) Self-compile an LE image that reverts the nvidia-legacy driver package to 304.latest, which is still possible to build/use as nVidia still maintains the older legacy driver against current mesa/xorg.
c) Stick with LE 7.0.3.