Things to try
-turn off wireless
-make sure power settings are for max performance
-run off outlet power and not batt (even with power settings at max my dell runs lower frames per second on the battery) You can get a cheap inverter for the car
-turn off any virus protection.
-turn off any/all background programs that arent 100% necessary
Speeding up your computer in general:
-dump norton or mcafee There are many free virus programs that are less demanding and very effective
-turn off system restore (I back things up on two drives manually every week - yes I'm paranoid but I'm ok with that)
-get rid of the fancy visual junk, folder display options etc
Obviously on the sim you can go in and lower all the parameters so that the graphics are less demanding
The ones that make the most diffence in my expereience are
-turn off particles
-turn off scenery detail or scenery objects and trees all together
More on speeding up your computer
http://forum.notebookreview.com/showthread.php?t=285280