Without mentioning any of the answers that you asked not to be mentioned, There are only a couple of ideas that I can come up with.
1. Go back to flying in FS 2002 until you can afford upgrades or a new computer.

2. Try lowering all of the settings to the very minimums and so a flight. After your flight raise the one thing that is most important to you. If scenery is more important than weather, increase scenery details. See how it works with another flight. then keep adjusting things until you get to a point that you can live with.

3. If you turn off things like antialiasing, reflections (If you can even have reflections with your video card), and 3D clouds performance will improve.

All in all you will have to make sacrifices, performance comes at the cost of quality. Almost everyone I know that uses 2004 has had to sacrifice some quality for performance. Personally I fly with little or no AI traffic to make my performance better. If I am useing real time weather or flying in really bad weather I turn off the 3D clouds. I know this is not the answer that you might have hoped for but beleive me I wish I could say "Download this little program and FS will run fully maxed out on any system!" I would be a rich man if I could say that.

Good luck getting it set up. And don't worry, alot of us can not afford upgrades for our computers but we try and make the best out of what we have.

Kevin

One more thing you can do is download optimized textures for scenery.There are such textures for trees,ground and clouds.Personally when I installed these textures for 3d clouds it not only dramatically increased perfomance-it improved 3d clouds look!

If you are seriously interested I can find links to these textures for you...

You can search the downloads on this site...everything here is absolutely free.

I recently downloaded some tree enhancements and got a huge increase in framerates and in visual quality...they made a huge difference.