I think your system can just about handle FS2K2 and although FS2K2 runs best with XP, XP can be very heavy on your system. Try the following: In control panel set your display to run at 16bit (medium) colour not 32bit (highest). Also under system properties, click advanced and adjust visual settings to give best performance. This will remove the really pretty face of XP to look like drab ol' Win2K but it will reduce the high RAM demand by XP. Also click on advanced and set processor scheduling and memory usage to give best performance for programs.
Basically that's all you can do with XP to run programs such as FS2K2 faster. Now turn your attention to FS2K2. Go to settings, display and turn down most settings to sparse. Do the same with aircraft and hardware. Set refresh rate to less than 20. If FS2k2 is now running fine though a little bland, slowly crank up display setting levels until you get to levels that do not cause any slow down. It should work. My PC at work is a crap/standard 1.8GHZ, 128MB no graphics card machine running XPpro but FS2k2 runs just fine after a little experimentation with the display and making the above settings on the PC. At home I have a Compaq Presario s5100nx 2.6GHZ running 640MB ram with an integrated graphics/video card and even running FS2K2 at max display setting bothers it not one jot!

I'm scared of heights....