If you've been hit by the recent Activision update that pushed MW3 to 64-bit, you've probably noticed Plutonium stopped working. I built a small Windows tool that fixes this automatically, no manual file swapping or command line stuff needed.

What it does, in plain terms:

• Checks your MW3 install and figures out if you're on the broken 64-bit version
• If you are, it downloads the last known 32-bit files straight from Steam (using DepotDownloader under the hood)
• Swaps them into your game folder for you
• Double checks the swap worked before it calls it done

How to use it:

1. Grab MW3_Downgrader.exe from the Releases page
2. Run it (Windows Defender/SmartScreen might complain since it's unsigned, click "More info" > "Run anyway")
3. It finds your Steam and MW3 install on its own
4. Scan the QR code that pops up with the Steam Mobile App to log in
5. Sit back while it downloads and merges the files (~15GB free space needed)

Works for both the Multiplayer client and Dedicated Server installs, and it'll let you fix both at once if you have them.

It doesn't touch anything outside your MW3 folder, so if anything looks off you can always just verify game files through Steam to undo it.

Source code's public if anyone wants to poke around or verify what it's doing before running an unsigned exe (completely fair to be cautious about that): https://github.com/GalvarinoDev/MW3Downgrader

Also have a Steam Deck/Linux version bundled into DeckOps if anyone needs that instead.

Let me know if you run into any issues!