Here is a step by step guide to multiplayer flying in FS2004, using the Inspire.net.nz server (which the Southern Hemisphere flight forum always uses also the old nzffac members ) as an example. If you are having any difficulty with this process, please post your problem in a reply below we are always willing to help ya out
Method 1) Connecting once inside your aircraft.
Step 1.
Start FS2004.
Step 2.
Create a flight somewhere in NZ and put your aircraft on the parking stand of your choice. Do not use the active runway in case somebody else connects at the same time causing your aircraft to crash into each other.
Step 3.
Go to the main FS2004 menu (hit ALT on the keyboard) and then select Connect from the Flights/Multiplayer menu
user posted image
Step 4.
Into the player name box put a name of your choice.
Into the IP address box put 203.114.130.15 (The Inspire.net.nz Server)
Click the search button, in the Sessions window the 'My Session' multiplayer game will appear.
user posted image
Click the join button and you will be in the session!
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Method 2) Connecting from the main FS2004 screen.
Step 1.
Start FS2004.
Step 2.
From the main FS2004 screen select Multiplayer and then Open Multiplayer Session.
user posted image
Step 3.
Into the player name box put a name of your choice.
Into the IP address box put 203.114.130.15 (The Inspire.net.nz Server)
Click the search button, in the Sessions window the Inspire.net.nz 'My Session' multiplayer game will appear.
user posted image
Click the join button and you will be in the session! Once you are connected a text box will appear and you can chat to other members via instant messaging or on teamspeak.
Please note:
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First up, select your aircraft as normal. Bear in mind though, if you select an aircraft that someone doesn't have installed on their system, you will appear to the other player as the same plane they are flying, or ... a Cessna.
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Two IMPORTANT settings when flying online are Ignore Crashes and Frame Rate. If you touch another aircraft it will cause a collision unless Ignore Crashes is off.
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When you connect to a Multiplayer session, all PC's interconnect with each other (so if you cannot connect check your firewall/router ports/Nortons etc), and data is transferred to each PC based on the number of frames per second the sim is rendering. PLEASE, set it to no more than 25.
and for teamspeak
"Teamspeak2", often referred to as TS can be downloaded for free at http://www.goteamspeak.com/index.php?page=downloads
If you don't have it already, the version you will need is called 'TeamSpeak 2 Client' which is listed at the top of the page linked above. The filesize is only 5.59 MB to download, and has a simple .exe installer to get it setup on your computer.
Once installed, double click the icon to open up the main screen. Click 'Connect' and then 'Quick Connect' from the main menu at the top of the screen:
A dialogue box will appear.
In the 'Server address' box, enter teamspeak.inspire.net.nz
Then Enter a username of ur choice
Leave the rest of the boxes blank and click 'connect'
Once logged on, you will appear in the 'lobby' of the Inspire TS server. Right click on the 'Flight Sims' title in the box on the left hand side and click 'Switch to channel'
Next, you will need to set up a 'push to talk key'. When ever this certain key is pushed, it activates your microphone and whatever you say will be heard by everyone else on the channel. When you have finished speaking, you let go.
To do this, go to 'Settings' menu and the top of the screen and click 'Sound Input/Output Settings'.
In 'Voice Send Method', select 'push to talk' then click on the 'Set' button and choose a key which you will press every time you wish to speak. A good key to use is 'Scroll Lock', as it has no assignment inside fs2004 and won't change anything in the sim when you press it.
Once you are ready to speak, leave TS running in the background open up flightsim and speak away!
IF you have any problems with Teamspeak or the sever stuff i mite be able to help , post below or get hold of me in pm
I still check from time to time..might join ya one evening 
ah all good fun..
