Always triliniear with AA disabled and use these 2 posts to set up drivers and Nhancer so YOU control FSX and not Nvidia
That is very important
http://www.simviation.com/cgi-bin/yabb2 ... 53/165#171
The driver and FSX settings are in the next post below the one in the link above
With one gig of memory I would say the Scenery Complexity slider should come down to 50-75% The rest of the sliders (other than water you can reduce to 1xhigh) should remain the same although you can also reduce the mesh complexity to 80% which may also help.
Turn off aircraft lables for AI too.