I apologize for posting this here, but I am not active in the Marathon community and I have no better way to contact you.

I also apologize for the incredibly specific nature of this message.

https://trilogyrelease.bungie.org/

At the bottom of the Trilogy Release page, there is a note that reads as follows:

Important Note:
This disc is included in .ISO format. It is beyond the scope of this page to walk you through using this format - Google is your friend. (Please don't write about this - we probably won't even answer.) For folks who don't have tools for mounting .ISOs, I found this page, with a link to a tiny, free, unsupported app available from Microsoft that comes with pretty simple instructions (though no auto-setup). I downloaded it, followed the directions to install it, and tested it - it works nicely. That's the limit of our tech support. If the day comes when the linked web page disappears, let us know and we'll try and put up a local copy of the tiny app.

The day has come. The linked web page has disappeared.

You’re welcome.