first go to this website enter your system features if there is one feature that you dont know or you are not sure just select:i dont know, the site will check the correct feature for you, then site is going to create an fsx.cfg file with new entries that are going to improove graphics and FPS based on your system then you can download the fsx.cfg file and replace it with the one that is on your temp folder dont forget to backup the one that you already have, dont worry the website is going to tell you how to find your fsx.cfg file, this is website link:
then here is a wonderful tool. Probably you have installed a multicore processor in your pc, as you already know FSX was created to run in just one core this tool is going to give you the option to get FSX running in up to 6 cores your sim will be smoother and will improove your frame rates.
here is the file i have uploaded it to my mediafire account:
1. extract the file
2. run the tool
3. click set file
4. click set executable file
5. browse your fsx executable file
5. priority high and boost enabled yes, then select core 1,2,3,4..........
6. apply settings , you can see 9 free spaces below, that is if you want to run another software at the same time like your internet browser or any weather tool, so those programs are not going to interfer with FSX
the tool comes with a better explained tutorial that you can check in a PDF file.
i have tried this and im more than happy with the results just setting your FSX.cfg file will give you a great upgrade if you really want to take the most advantage try the whole thing, if you have a question let me know. thanks