bocardo :
One more thing, is there anything I should know about switching vendors (nvidia to ati).
Any procedures to avoid problems when changing the drivers or stuff like that?
Nope! Not really. When you install new video drivers, the previous drivers are over-written. Also, remember to uninstall the Utility Manager of the previous card and after you install the drivers from the CD for the new one go to their website and DL the latest drivers/software.
Another good thing that you can pick up is Driver Sweeper. It scans your computer for drivers and you can select to remove them completely. Sometimes when you just install and overwrite drivers there are traces of the previous driver. With video drivers, sometimes you might be playing a game and a major framerate drop will occur, or you will have other video issues.
Here's a link to DL Driver Sweeper, in case you're interested.
Driver Sweeper
Just scroll down the page and click "I Agree" and it will begin the DL automatically.
Hopefully this info helps!
-Charles