With the nvidia proprietary drivers, you don't want built-in framebuffer support. If the question is how to change video DRIVERS from vesa to nvidia, that is specified in the xorg.conf file. In the Device section, the Driver line should read 'nvidia' and not 'vesa' or 'nv'.
If I've misunderstood, or if you are still stuck, please post again, and include the results of this command run as root:
Code:
glxinfo | grep direct
and paste your xorg.conf file in here too.