The Wikipedia backwards compatibility list after years of what amounted to vandalism (People for years were adding things that worked on their hacked 360, games were listed that weren't noted as working in any region, and other such nonsense.), was cleaned up a year or so ago for at least the North American list (Unsure about Europe/Japan).
So that list is now accurate and based off Microsoft press releases. And even games like Tecmo Arcade Classics that officially disappeared off the list yet still work (I suspect that one was due to the bug that never got fixed that made it work only if your 360 was set to SD/ED resolutions), are noted the last I checked. I think even Richard Burns Rally is listed as compatible in North America thanks to sticking so close to official Microsoft data to restore the list, despite the fact that the publisher cancelled production of the North American localization the day before the disc replicating plant was to make the North American discs. It had already joined the BC list in a slightly earlier update before its scheduled release, so it's listed despite never being available to NA consumers.
I like to say that 10% of the Xbox library was truly compatible. 50% won't boot on an unmodified 360 and of the other half that did work, I'd estimate based off spending time in 30-40 games through the years when bored (I own several original Xbox systems, so I've never relied on the 360 for playing original Xbox games), that only 20% of those that officially work were problem free enough to be worthwhile playing on a 360. It's a nice option here and there, but much like the Xbox One's excellent original Xbox compatibility, it's only a solid option for a small subsection of the library.
Incidentally, I'd bet good money that Torrax called it. That's the obvious answer after the topic creator said he's using an unofficial HDD. The hard drive bootleggers always left that partition off.
Someone correct me if I'm wrong (it's been a while), but I believe each game needs to be patched individually as well, requiring you to have your 360 connected to the internet when you insert an original Xbox disc. I remember back when I used the feature, each compatible title would download a small update file before the game would work.
I believe when he gets his HDD situation sorted, inserting one original Xbox game off the BC list on a system connected to Xbox Live should trigger the full collection of emulation profiles to install to his HDD's backwards compatibility partition.
Edited by Atariboy, Wed Mar 13, 2019 2:38 PM.