Your problem is clearly that your hardware is not really up to FSX. Your system is similar to my last system so you are going to need to keep the autogen and the scenery complexity no higher than medium.
FSX is much more CPU dpendant than GPU dependant and it is your CPU holding you back rather than your GPU.
You could try using the usepools=0 setting, not usually recommended for 512 meg graphics cards, but I use it OK so long as I don't ovr push the sliders to much. I think that may work well for you (but if FSX crashes too often, you may have to revert to usepools=1).
Really, the best thing you can do, I think is have a go at overclocking your CPU a bit. Google overclock and your CPU and see what settings and overclocks others have been getting. Even a 10% to 20% overclock will make a difference, just don't go the whole hog all at once and download 'Coretemp' to keep an eye on how hot thngs are getting.
Personally,I wouldn't waste my money on fsx pc booster as if you take the time to search/read the forums, all of the tweaks it contains can be found (subject to a bit of trial and error here and there).
Other than that, you can research theservices Windows is running in the background and perhaps some of the non Windows services you are running and try to trim them down to a bare minimum. Run FSX with your antivirus off (provided that you are not on-line) and turn off any other scanning, anti-malware, etc. services you may be running.
Run task manager and post a screenshot of it here, so we can see what background processes are running and perhaps suggest some that you can trim. My Windows 7 is only running with 2 services (plus quite a few associated with my antivirus). I bet you are running 60 or 70 (which can cripple a low end system).
Q9550 @ 3.78 GHz with Gainward GTX570 1.25 Gig DRAM
4 Gig DDR2 RAM - Windows 7 64 Bit
Resolution 1680 X 1050 X32