I know I've posted things like this before, but I'm getting desperate to get FSX to run faster. It was running fine for awhile, but then I started out flying on a very foggy day and the FPS slowed to a crawl. Is there anything I can do to make FSX run faster short of a system upgrade (which I might have to do in the end)?

My specs:
-Computer: Dell Inspiron 1720 (laptop)
-OS: Vista 32-bit SP2
-RAM: 4 GB
-Processor: 2x (Dual core) Intel Core2 Duo CPU T5250 each @ 1.50GHz
-Video Card: NVIDIA GeForce 8600M GT

Thanks,
boeing247