Posting this in here because it's ridiculously easy to set up Halo 1 and 2 online in CURRENT YEAR
Halo PC/CE
Halo Combat Evolved was released in 2001 on Xbox and again in 2004 for PC. What sets the PC version of Halo apart from its console counterpart is the ability to play multiplayer online, as well as modify a special Custom Edition.
Functioning base game: Custom Edition for convenience:
http://hce.halomaps.org/index.cfm
Manual update for "unofficial" copies:
http://halo-fixes.findforum.net/t6-manual-1-10-update-for-players-with-unofficial-copies
You should be able to just plop the updates into where Halo or HaloCE was installed and they should function online. If you don't see servers, check your firewall settings and make sure no other program is using the network (which should be common sense lol)
Halo 2
Halo 2 was literally repackaged for Windows Vista as a cash in/"incentive" to use Microshaft's
shinyshitty new OS, though due to the OG Xbox Live having been shut down years ago and with the existence of Project Cartographer, Halo 2 Vista is basically the way to play OG Halo 2 online these days.
Halo 2 ISO:
http://www.mediafire.com/download/6k6go3g5r5oc5ap/Halo+2.iso
Project Cartographer (basically a must for those weirdos who still play Halo 2 in 2017):
http://www.h2v.online/install/
Because Halo 2 is poorly optimized, making this game run optimally may literally require changing some compatibility settings.
After installing Halo 2, put Project Cartographer (Halo_2_Launcher.exe) in your Halo 2 folder and run it.
Register an account for online play, log in, and launch the game. Test the first minute or so of the campaign before doing anything else.
If you have framerate any lower than 25 at the lowest settings, I have a trick for you.
Go back into your Halo 2 folder, right click on Halo2.exe, and go into properties.
Under the Compatibility tab, check the following:
-Run in 640 x 480 screen resolution
-Disable visual themes
-Disable desktop composition
-Disable display scaling on high DPI settings
-Run this program as an administrator
Open Halo_2_Launcher.exe and click on Settings
Under Resolution, type 640 for Width and 480 for Height
Set the Window Mode to Borderless, or if that doesn't work set it to Window
Turn VSync off
You can turn the Intro Video off as well if it's annoying
If you did any of this correctly, you should be seeing servers you can connect to ingame.