|As most people with Nvidia cards are probably not aware, the new free and open source driver Nouveau is already enabled in Aptosid kernels, and does work well for most cards and use cases. So, it's time to finally get rid of the closed source malware, and potentially problematic 3rd party repositories. Here is how to do that:
In KDE System Settings turn all desktop effects off. Remove all 3rd party repositories from /etc/apt/sources.list.d/. Remove all traces of nvidia in: /etc/default/dmakms, /etc/X11/xorg.conf.d/ and /usr/src/.
apt-get purge ^nvidia* ^libnividia* xserver-xorg-video-nv
apt-get update && apt-get dist-upgrade
apt-get install --reinstall xserver-xorg-video-nouveau
Reboot. You are using the free open source Nouveau driver now. Please post any issues you might have with this HowTo.