How can I transfer a Steam game's program files from one PC to another?

[SEGA_Genesis]

I have an old Dell Optiplex gx280 I'm turning into a childhood gaming rig and there's a few Steam games I would like to play on it. I was able to install Steam and get it running due to posts/videos from the community on here and YouTube, however while I'm able to log in and message friends I can't download games from my library (expected, this version is 5 years old).

I copied Portal and Fallout 3 over from my Windows 11 rig to begin with, copying the entire folder from steam/steamapps/common but I can't get them to boot either through the launcher (which doesn't recognize them as installed and just queues them if I try) or through the folder.


Am I forgetting to copy over certain files, or could the issue be with the programs I'm putting on the PC? Is there something else I should try?

I haven't been able to find any guides to sideloading Steam apps, and to clarify both PC's are logged into my account and I have ownership of these games. I have not tried installing versions of these games from 2018 yet so I'll try that next if I'm not missing any files to transfer.

Thanks in advance and I hope I explained it well enough.

[ReBoot]

Make sure both PCs are in the same network, start Steam on both PCs, make sure you DID NOT disable the option for local transfers, start downloading. Steam will then transfer game over the network itself. No need to do any manual steps, just let Steam do everything for you.

[MancSoulja]

You need to copy over the games manifest files. You'll find them in the root of Steam's common diretory.

They look like this "appmanifest_107410" With the digits at the end being the game's AppID.

You need to find the file that corresponds to the game you have copied over so for Fallout 3 you'd need the file appmanifest_22300 as 22300 is the AppID for Fallout 3.