You should be getting alot more FPS. I get between 21~30 (limited @30) with a simular computer.
No, 64bit won't help, FSX is a 32bit DX9 game. Have you installed service pack (SP1)? that helps some in FPS. You might try choking back on AIs, that's been the biggest FPS hitter for me. I also installed GA Traffic and now there's so much chat on 122.9, I can't talk to the tower!
Here's what runs the game well for me, At least when I stay out at regonals.
GRAPHICS
Target frame rate: 30
Full screen res: 1680x1050x16
Filtering: Trilinear
Anti-aliasing: on
Global texture resolution: High
Lens flare: off
Light bloom: off
Advanced animations: off
Informational text: Continuous
AIRCRAFT
Default cockpit view: 3-D virtual cockpit
Show cockpit ToolTips: off
High-resolution 3-D virtual cockpit: on
2-D panel transparency: 0%
Aircraft cast shadows: on
Aircraft casts shadows on itself: off
Aircraft landing-lights illuminate ground: off
SCENERY
Level of detail radius: Medium
Mesh complexity: 51
Mesh resolution: 19m
Texture resolution: 1m
Water effects: None
Land detail textures: on
Scenery complexity: Extremely dense
Autogen density: Extremely dense
Ground scenery shadows: off
Special effects detail: Low
WEATHER
Cloud draw distanse: 60mi / 96km
Thermal visualization: None
Simple clouds: on
Download winds aloft data with real-world weather: off
Disable turbulence and thermal effects on aircraft: off
Rate at which weather changes: Medium
TRAFFIC
Airline traffic density: 0%
General aviation traffic density: 100%
Airport vehicle density: 0%
Road vehicles: 100%
Ships and ferries: 0%
Leasure boats: 0%
Show aircraft labels: off
With this computer:
Intel DP965LT ATX mainboard (P965express chipset)
Intel onboard Azalia sound & 82566c LAN
intel Core2Duo E6600@2.4ghz
Generic intel approved thermally advantaged ATX case
Thermaltake 775D copperbase heatpipe cpu cooling fan
Corsair 4x1gb duel channel DDR2@667mhz note#1
Gigabyte nVida 8800GTX w/768mb DDR3
Memorex DVD-CD R+RW drive
Western Digital 1600YS SATA hardrive
Antec NeoHe 500watt power supply
Samsung 215TW 21" widescreen (1680x1050) DVI LCD
Samsung CX213TW 13" DVI LCD
winXp SP2