Ok, time for another of my essays on Flight sim
To start with, the best way to go about this is to download a aircraft designed specifically for the version of FS that you have. You can use fs5, fs95 and fs98 aircraft with fs2000, howevere fs5 and fs95 aircraft will need to be convertered. I dont recommend you use aircraft for fs5 and fs95 as the flight dynamics leave alot to be desired by todays flight sim standards. They are also alot more complex to install.
FS98 aircraft will work with fs2000, the only downside is the technology at the time of fs98 was rather limited in terms of animation of aircraft parts and visual models. The flight dynamics were alot better than what they used to be and by far more accurate. Basically as I said the best way to go about getting new aircraft for FS2000 is to download FS2000 planes.
Now we come to installing the aircraft. Thankfully the majority of aircraft designers on Flightsim.com have sorted the files into their respective directorys inside the zip file. This makes life very easy when it comes to installing because it basically means that you have to copy the files straight to the Aircraft Directory of FS2000. That method will work if the designer includes the main directory for the aircraft in the zip file. By this I mean the directory which contains the panel, sound, model and texture subdirectories. If the designer hasnt included this directory then you have to create it. This is easy. Simply goto your FS2000 Aircraft directory and (if your using windows explorer) rigth click inside that directory and select New Then select Folder. Name this folder according to the type of aircraft your installing. Then unzip all the files to this directory.
Now the hard part. If the designer hasnt included any directorys at all you need to create them all yourself. Repeat the process for creating a directory in the FS2000 Aircraft directory and then inside this directory create 4 new directorys called panel, sound, texture and model.
In the sound directory put the sound.cfg file and if the aircraft comes with sound files, put all the *.wav files in this directory as well.
In the Panel directory put the panel.cfg. If the designer has included a panel and not sorted the panel files either into a directory or separate zip file, get rid of this particular aircraft and download another, it simply too hard to determine which files are for the panel and which are aircarft textures.
In the model directory put the model.cfg, *.mdl, *.mpi and *.nmp files. Note that not all aircraft will have all these files.
Ok, I think thats about it, if you have any further problems let me know