Have you tried uploading those DLLs to VirusTotal? In case you're not familiar with it yet, it's an on-line free virus scanning service owned by Google. It'll use a large number of different virus scanners, including all of the well-known ones, to scan your upload for possible malware. You can also see if the file was already uploaded by someone else and scanned earlier.

Of course even if none of the virus scanners at VirusTotal find anything, that's still not a guarantee that those files aren't malicious. But it's better than nothing.

That's a good idea. However I also found that one of my work laptops (*cough*) still has a Steam build from January. I'll try that one first.

Update: Alright some progress. With my backup and some trial and error I was able to figure out that the following files need to be replaced with older versions in order to make Steam start under Windows XP x64:

1steamui.dll
2steamclient.dll
3bin\serverbrowser.dll
4bin\friendsui.dll

Also Steam needs to be started with the following CLI option to prevent the self-update:

1-noverifyfiles -nobootstrapupdate -skipinitialbootstrap -norepairfiles

However I started HL2 which froze my complete system after the Valve logo. Some more investigation is required unfortunately.

Also I wonder: Am I allowed to post links/upload these DLLs here?

gordon-creAtive.com wrote:

Also I wonder: Am I allowed to post links/upload these DLLs here?

That would be legally questionable. But instead, you could just share the SHA256 checksums here. 😀

HL2 doesn't need steam if you use the -game switch
Running online DRM games offline guide

Make sure you disable the steam service

I revisited this topic as I figured out that Half-Life 2 freezing in the game menu was caused by my SLI setup and not by Steam. I managed to get Steam working in XP x64 with the following steps:

1. Get an up-to-date installation of Steam from a supported system.

2. Replace the following files with older versions, these are the versions that work fine for me:

1NAME						VERSION				SHA256 SUM
2Steam.exe					04.89.17.15			929ca6eb0dfc38e8276c10c169d74f90c0642c92e28a253a3b3f4db9af0c93b9
3steamclient.dll				04.89.17.15			91fb428a392bfa4e83a8fcfb56cfac9802a1558742b267fcb96726079a32d3cc
4SteamUI.dll					04.89.17.15			01873c9ea56fcd7f11af2fc93e92bd007fb636440f1416b4e58e56eaf1319129
5tier0_s.dll					04.89.17.15			6ed50ffe1224da2962361249d4bbc310d060381e5087a2effcfafdfb24237539
6bin\chromehtml.dll			no version given	7475226a210e605787d90f03d6da8084b77e5ee57d3d6ff57b22de06cd16168a
7bin\filesystem_stdio.dll	04.89.17.15			1c0b3f3cf0e5e566e67cd5b3d27497a277dc7ab84ae90fb8897b0d5c65f2e7b2
8bin\friendsui.dll			04.89.17.15			b3ef3ea30d353261d6bf2dafb016c9fb183562de9a5f3e364568468788e3ca14
9bin\serverbrowser.dll		04.89.17.15			9c24ac4a9794a6f856731db8adc0926adbc2110c803986355a215317c751446e
10bin\vgui2_s.dll				04.89.17.15			3f4ce900b64290d58e16591cebf283b4c237feb661fa361da147e4a46924f0e2

I will not provide you with these files, even if you ask via PM.

3. Start Steam like that:

1Steam.exe -noverifyfiles -nobootstrapupdate -skipinitialbootstrap -norepairfiles

Make sure to not start it without these arguments, if you do it will update itself and you have to start over. Pay extra attention to the shortcuts that Steam creates for games. If Steam is not running and you launch such a game, you effectively launch the Steam without these arguments.

I was able to update games with this setup, L4D1 multiplayer worked fine and so did HL2 singleplayer.

Steam will download an update for itself and ask for a relaunch eventually, if you reject it, you should be fine.

I did some more research. I figured out that adding

1-overridepackageurl

to the launch arguments will prevent Steam from downloading its update, even when you force it to with the menu.

However I also noticed that Steam will reset its protocol handler "steam://" every time it's launched, it will even figure out if Steam.exe has been renamed. Steam uses the protocol handler for desktop shortcuts, so "steam://rungameid/220" will launch HL2 for example. See Steam Browser Protocol for details. What a huge PITA!

So here is what I came up with. I wrote a really short C# application that acts like a proxy for Steam.exe. Rename your original Steam.exe into "Steam.original.exe" and drop the Steam.exe attached to this post next to it. It will:

1. Reset the steam:// handler to itself
2. Start steam.original.exe with the arguments "-noverifyfiles -nobootstrapupdate -skipinitialbootstrap -norepairfiles -overridepackageurl" as well as all arguments provided to the proxy
3. Wait for Steam to stop running and reset the steam:// handler again

If you shut down your computer with Steam still running, the steam:// handler will not be reset. I'm looking into that later. If you start this proxy with Windows you should be relatively safe though.

Update:
It seems like I've finally found the hassle free and simple solution:

1. Get an up-to-date installation of Steam from a supported system.
2. Downgrade the necessary files as listed in my previous post.
3. Create a file in your Steam root directory called "steam.cfg" with the following content:

1BootStrapperInhibitAll=Enable 
2BootStrapperForceSelfUpdate=disable

4. Forget all other stuff I posted xD
5. Use Steam as usual.

This method has stopped working again, Steam just hangs after logging in. However I found another way to "run" Steam on XP. There is an application called "SteamLite" that provides basic Steam client functions over a CLI interface and there is a version compatible with XP. The setup is not that straightforward but easier that the previous method:

1. Make sure you have Internet Explorer 8 installed.
2. Control Panel > Internet Options > Advanced > Scroll way down > Enable "Check for Server Certificate Revocation".
3. Install up-to-date Certificates.
4. Get the steam Setup.
5. Install Steam. It may hang when creating the desktop shortcut, just kill it with the task manager.
6. Start Steam and let it update itself. Once finished it complains that XP is no longer supported. Give Steam the finger and click "OK".
7. Find "SteamLiteXP" on the internet. While the application is perfectly legal (you can't pirate Steam games with it) it is distributed on a Russian piracy board that specializes in Steam. So no links here unfortunately. The SHA1 sum of version 1.1.6 is "8650f8c42644151defaa02b434941d6576315f7b".
8. Move "SteamLiteXP.exe" to your Steam root folder.
9. Run it and follow the instructions.

Also make sure to read the instructions in the text file that comes with SteamLiteXP.

I was able to launch and play Left4Dead 1 online with this.

Does anyone have Steam working on XP without SSE2? I got a 2016 build installed but it seems unable to communicate with Steam even with updated root certs.

Do you mean "Steam" OR "SteamLiteXP" ?

gordon-creAtive.com wrote on 2020-06-15, 12:52:

Do you mean "Steam" OR "SteamLiteXP" ?

Either. However, I believe the reason my method wasn't working before was that I was actually using a build from October 2013, not 2016. I checked the signing times of the Steam dlls and they're dated 2013. I believe I can get it to work if I have a copy of the client-download.steampowered.com/client/* packages from ~Oct. 2016 or a copy of the Steam client from around then. Someone linked a version here but the link is dead...

Edit: so the Nov. 2018 client seems to work fine for the most part but I have the connection issues that everyone else has with it as well. I've tried updating networking_config.json and config/config.vdf to without many results. Looking in netmon it seems like Valve and my XP machine are talking back and forth, but not much is being done apparently 😁

It seems like the latest versions of SteamLiteXP don't work without SSE2...

EDIT 2: The Steam build from 2014 in the reviews here https://archive.org/details/steam_201901 is able to login but not download any games (content servers unreachable).

EDIT 3: The Steam build from 2014 is fully usable as long as you can install the games on another machine (or use SteamCMD elsewhere) you can copy their folders in steamapps/common as well as their appmanifest*acf file in steamapps to your XP machine's library and they'll launch fine! Was able to connect to VAC secured HL servers.

EDIT 4: SteamCMD also seems to work, so you can use that to update games (at least with the POSReady TLS 1.2 update).

Is some build still working for games downloading? If yes pleas upload it to some cloud share. I dont care about SSE2..

No one has been able to login with any version of the official Steam client. Try SteamLiteXP, it supports downloading.

Are using Steam LiteXP? i saw some video it looks command line only (=PITA)
https://www.youtube.com/watch?v=J7n6VQqfXbg

It is. But for me that‘s better than not being able to use my Steam games at all.

Hmm 2 week ago still worked full blown side-loaded version, in theory if cmd line interface is working someone can write some GUI frontend for it.

Side-loaded version of which application?

https://archive.org/details/steam_201901

Is someone using SteamLite for longer time? I not paranoid but i wouldn't be totally surprised if someone would try to steal some Steam credentials through it..

BTW SteamLite:
https://cs.rin.ru/forum/viewtopic.php?f=29&t=68783

Minimum System Requirements:
Windows Vista: SP2 + IE9 + KB2533623 + KB2868626
Windows 7: SP1 + IE11 + KB3020369 + KB3125574
Windows 10: January 2020 Updates
Checking for server certificate revocation must be enabled in internet options

Does it means that some old version is needed for XP or its not only officially supported?

Update:
Yeah, there is older version for XP only :
https://cs.rin.ru/forum/viewtopic.php?f=10&t=98620

Trying a different approach.

Anyone had any luck with "steam emulators" or any other ways to simply download the games in Linux or Win7+, remove the DRM and then move them to the WinXP machine?

How about SteamCMD on XP?

I have plenty of games on my Steam account that suck on modern windows and are even too much hassle to play in WINE but I still like to play them from time to time in their original forms.