Mavrickarrior, I am going to post this one more time for you.
Please try to read thoroughly and understand everything I am posting here and now.
1. In order to play online, you need a clean, vanilla CFS3 install, fully updated to 3.1 an 3.1a.
Updates can be obtained here:
http://www.microsoft.com/games/combatfs3/
Note: Install 3.1 before installing 3.1a.
Note: You must have the exact same aircraft as the host, or you will not be able to join a game. Similarly, if you are hosting, anyone trying to join your game must also have the same planes, so if your install has extra aircraft, please make sure to not to allow them in your game. Look on the Host Game section on the MULTIPLAYER tab.
2. Joining a game is the easiest. Click on the MUTIPLAYER tab and select JOIN PRIVATE GAME. Type the intended IP into the box, and then join.
3. In order to Host a game you, must open your router ports (port forwarding). You may also have to turn off your anti-virus program, on some cases.
4. Windows XP is no problem. CFS3 was written to XP in the first place. Vista is a problem. You can neither host nor join through Vista normally. There is a fix. Please read Post #1 in the following thread, and follow the instructions exactly:
http://www.sim-outhouse.com/sohforums/showthread.php?t=9007
If you are currently having problems, I highly recommend a complete re-install of CFS3.
Do not use the uninstall option, just delete it.
You will also have to delete the two Combat Flight Simulator 3.0 folders from Application Data/Microsoft and My Documents folders.
In XP, you will find those two Combat Flight Simulator 3.0 folders at these two locations:
1. C:\Documents and Settings\User Name (Your Name)\Application Data\Microsoft
2. C:\Documents and Settings\User Name (Your Name)\My Documents
In Vista, they are here:
1. C:\Users\\AppData\Roaming\Microsoft
2. C:\Users\\Documents for My Documents
If you can't find the Application Data folder in XP (AppData in Vista), please do this,
in XP: Open any Window, click on the Tools tab at the top of the page, and select Folder Options from the menu. Click the View tab on the new screen, and look down the list for Hidden files and folders. Mark the Show hidden files and folders line on the list.
Look below that for Hide extensions for know file types, and uncheck it.
Then click Apply and then OK.
In Vista: Open a folder, say My Documents, for example. At top left, click on Organize and then Folder and Search Options. Click on View and you will find both selections in the list.
I hope this helps.:d