When you re-installed the drivers did you run driver cleaner first? as i found that the best way of removing all evidence of your last videocard.
What i would do is download the Nforce drivers for your motherboard.
The latest drivers for your videocard (You have anyway)
and then go into safemode and remove all traces of your old nforce and all the nvidia video drivers via control panel.
Then i would run driver cleaner
http://www.driverheaven.net/cleaner/
Let it get rid of anything to do with nvidia video and nforce.
Then run the new Nforce drivers first then the latest detonator drivers and restart the PC.