I would recommend NickN guide to any beginner in tweaking fsx and windows but for me only some of his tweaks are good for me as now i tweak fsx in a different way to almost every one in order to balance the performance of fsx and my pc and it works really well for me :)

The best thing i can recommend to every one is.. don't fly the fps counter.. fly the sim or you will end up like i did.. endless tweaking and re-installing which takes you away from the the beauty of flying in the sim.

Scott, LOD does not need an ultra fast cpu or mega over clock. Ive stopped over clocking as i don't need it and my current cpu is slower than the over clock i had on my old one ( over clocking can help and im not anti over clocking to boost fsx performance ). Ive tweaked enough to fly at almost mach 1 in the IRIS F16 using REX clouds in low/poor visibility at just over 500ft agl in the Orbx Seattle region and the ground textures can keep up.

Anything is possible in fsx but its a balancing act with the hardware you have and what you are trying to do with the sim. I don't fly the lonely planet so i always have AI running in the shape of UT2 :)