DennisRSimonsen :
USAFRet :
http://forums.steampowered.com/forums/showthread.php?t=2965732
I dont want to remove hole steam, only bo3
From that link
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Simple way how to properly MOVE already installed game to other drive
1. in Windows: copy game folder to your steam games folder on other drive
2. in Steam: uninstall the game (right click on game and choose: delete local content)
3. in Steam: install into other drive (where you've already copied the files)
Steam will just verify that all files are present and change its settings, registry setting and any other settings that point to game location.
4. Done. No download necessary, no manual changing of settings.
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Basically:
Create a new folder on the other drive
In the Steam client, tell it about that folder
In your current Steamapps folder, find the BO3 subfolder.
Steamapps/common/BBO3
Copy that BO3 folder to the new one you made earlier.