I hesitated to make this thread, but ultimately think the issue separate enough from the Latest Version of Software Running on XP thread (and the various Steam threads left hanging from recent history) to warrant a thread of its own since the Latest Version thread is mostly focused on productivity software and because I hate waiting half an hour downloading a game only to find that it doesn't even work.
Steam lost XP support in 2019. Since then, multiple solutions have come up with varying levels of success. After trying 2 other avenues, I used the method described in this video to install Steam on XP because, while it's uncomfortably unfamiliar (they say this Steam rebuild has multiple patches, but only name one of them), it's the only way I got games to download in-client. Another method from December 2020 in the comments of this post claimed to do the same, but it didn't work for me, though this may have been because of an error I made midway.
Anyways, this isn't for discussing Steam compatibility as much as it is for Steam game compatibility. Some games on XP claim to be compatible (or at least logically should be compatible) but aren't for a variety of reasons. Some games even used to be XP-compatible, but have somehow lost this after newer updates that, due to the nature of Steam, are entirely unavoidable. With this thread, I aim to create a more uniform list of what is and isn't working on XP in 2021 and beyond. So far, this is what I've found:
- SteamVR is not compatible. Attempts to install will only restart Steam.
- For all hl2-era games, your game may render itself sideways for some reason. If this happens, change your video setting to the lowest possible setting on 4:3 mode, then change it back to the resolution and aspect ratio you prefer to play at. Closing the notification you get about screen resolution from Windows is fruitless, since it comes back instantly. Attempts to change your in-game volume settings will not last after closing the game.
- Team Fortress 2 is not functionally compatible. The game will run, but it doesn't connect to Steam, so you lose your overlay, your inventory, the store, and really everything in the game that isn't the main menu. Starting your own server ingame crashes before reaching the team choice screen. I'm going to try one last thing (getting a Steam invite and trying to join the game through that), but otherwise I don't know of any way to make it work that wouldn't require modifications. I guess if you wanted to take the commentary tour, you could try that?
- Garry's Mod is not functionally compatible. After it flips your screen sideways, it gives you a bug warning in a standard MessageBox window about how to report bugs to the team. I may try some testing later with the facepunch common issues guide, but will wait on confirming things with TF2 first.
- Half-Life is fully compatible, even online multiplayer.
- Half-Life 2 is fully compatible.
- Portal 2, afaik, is fully compatible.
- Poker Night at the Inventory is fully compatible, though I don't know if it gives TF2 items due to aforementioned issues. Even though Steam overlay doesn't work with this game, you will still get achievements.
- Audiosurf is fully compatible, though I haven't tested the login feature.
- Crazy Taxi is fully compatible.
- Lethal League is not functionally compatible. You can hear game audio and control the menu, but the game will only display a series of scattered pixels that don't move. I haven't tested to see if resolution adjustments or menu choices will remedy this.
- Ultimate Custom Night, in a strange twist of fate, is fully compatible despite being released in 2018.
I have other games I could test, but those are all I've covered for now. If anyone has anything else to test, or weird workarounds that could fix any incompatibility with the above, do share. Also, a game that only works when cracked doesn't count as a compatible game. You're aiming for things you can download legally with the Steam client, and nothing else.