A couple of files I recommend to help performance

[jordonj]

fsautostart: this neat little utility shuts down all those processes in the background, making your flying experience that much smoother.  It takes some time to configure, but it's a step-by-step process.  The window where you determine what to shut down has a window next to it telling you what to shut down and what to leave alone (it worked GREAT for me).
You can find it here:
http://www.fs-gs.com/downloads.htm

The No-CD Override:also improves performance. (at the very least, you don't need to change CDs!)  This is NOT a crack and doesn't allow illegal copying.
Can be found here:
http://www.simviation.com/fs2004utilities1.htm

[Ivan]

No-CD patch decreases loadtime... spinup takes at least 2 seconds on a 52x drive

[Delta_]

I use both of those, and agree they are good.

[VPA_KTPA]

Yep there both keepers.i was getting decent performance with out either of those but every little bit helps.but the no cd tweak keeps that disk from getting scratched up.ouch now that would hurt if that disk ever got damaged.so i would say get them both and put that disk 4 up in a safe place.in the long run youll be glad you did.

[jordonj]

Another thing that helps to improve performance (on all games) is to configure the appearance for best performance (get rid of the romper-room look, the shadows, etc.)  I also ditch unneeded services.