Try "compressing" the FS folder. It seems counter intuitive to compress a folder that you always use, but it actually does work. I've seen this in several forums and it truly does work. I went from running normal planes at about 17-26 fps, down to 9-15 in high traffic, up to 20-30 and 15-25 respectively.
In Windows XP, browse through my computer for the FS9 main folder. Right click on it, and go to properties. On the first tab there is an "advanced button" click on this, and check the box marked "compress folder". Hit OK, and then "APPLY". This can take between 1 to 2 hours, so be patient. Once it's done, you'll have your simple solution, without sacrificing load time.
Captain
Chief Captain
First Officer