With the newer nvidia drivers (i forget what version it started with) you need to uninstall from your OS's Control Panel.
You can not roll back any more using Device Manager as this will cause nothing but problems. Do not uninstall the drivers
first, uninstall PhysX, 3D driver, HD driver and Nvidia update first, then uninstall the display driver. Before you reboot, go
and delete the Nvidia folder under your "C" drive. A good thing to do before you start uninstalling anything is to make sure
everything else is updated. (OS, any 3rd party apps.. Nvidia Inspector, MSI's Afterburner, EVGA's Precision tool ect.)
There is no need to use a Driver Sweeper any more, although if you do it won't hurt anything. When you start to install
the new driver use the Custom install method and only install PhysX and the display driver. If you use Nvidia 3D glasses
then install that driver or if you have a mobo that supports the HD driver. The Nvidia update can be installed but really no
need for it, plus its just another app running in the background.

To the OP, did you check the AA box in FSX? On my rig i need to have that checked in fsx or i have the jaggies big time.
I haven't tried these new set of driver yet, just put in the 296.10 drivers 2 weeks ago and they are pretty good.
Joe