Yep. Its because its a laptop. I use one to run FS as well, and there are a few things you can do to overcome the issues.
The first is to know how much RAM you actually have. You need AT LEAST 256 to get this to work right. Any more and you're not gonna get squat.
Next you need this program:
FSAutoStart by Ken Salter. You set up the program to shut down all non-FS programs and services, then start it up. It shuts them down, and then starts FS. When you exit FS, AutoStart starts everything back up, so your computer is running exactly the same way it was before. It does have a couple of issues with things like firewalls, but if you're running XP this shouldn't be a problem.
And finally, you need to set up FS so it will run on your computer. Just get into FS and fly somewhere that lags really bad (big cities). Now start messing with the sliders in the display menu. Get FS to run with a minimum of 12-15 fps in the cities, and you'll get great framerates out in the rest of the world.