I was wondering if there is some registry key where I can disable the option for the user to turn off message history logging?
Thanks

No, there is no registry key which will prevent the user to turn on/off Messenger logging.

Even if there was a registry key to prevent it, it would be relative easy for the user to delete such a registry key so that he could turn that option off again. And/or the user could always manually set the registry key MessageLoggingEnabled to REG_DWORD 0.

In other words: there is no way to force Message logging! It will always be a choice of the user.

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In Windows Live Messenger, the options under Tools > Options > Messages > Message History can be found in the registry under:

HKEY_CURRENT_USER\Software\Microsoft\MSNMessenger\PerPassportSettings\<Windows Live Id Hash>\
MessageLoggingEnabled
MessageLogShowHistory
MessageLogPath


1. MessageLoggingEnabled
Type: REG_BINARY or REG_DWORD
Description: Key for the option "Automatically keep a history of my conversations"
When logging is disabled this key has a REG_DWORD value of 0.
When logging is enabled this key has a special REG_BINARY value. Dunno what the value represents but it might be some kind of encoding/hash.

2. MessageLogShowHistory
Type: REG_DWORD
Description: key for the option "Show my last conversation in new conversation windows"
When you have disabled this, the registry value is 0.
When you have enabled this, the registry value is 1.

3. MessageLogPath
Type: REG_SZ
Description: key for the option "Save my conversations in this folder:"
This key holds the path where the log files will be saved.

4. MessageLogVersion
Type: REG_BINARY
Description: this key does not have an associated option in the options panel of Messenger. It contains the type/version of the log files. Format is unknown.

Thanks for the reply. I have just found that Messenger Plus is installed. Here you can also enable logging and you can password protect the settings, so the user can't change them

Sorry, but the user can always change it, very easly.

First of all, the things I said about manually editing the registry also applies to Messenger Plus! settings. All it takes is changing 1 registry key to disable chat logging:
HKEY_CURRENT_USER\Software\Patchou\Messenger Plus! Live\<Windows Live Id>\Preferences\EnableChatLog
No matter if you have protected the options with a password or not.

Second, the password protection of preferences in Messenger Plus! is extremely weak and is only there for 'accidental changes'. Again, all it takes is deleting one registry key to have access again to the preferences via the UI of Messenger Plus! Live:
CookieRevised's reply to Preferences Password

Third, Messenger Plus! must be installed and running in order to log messages with Messenger Plus!. It is again very easy to disable Messenger Plus! Live.

Fourth, the user will always be able to disable chat logging, even if the options are locked with a password, by simply unticking "Enable Logging" in the Plus! menu.

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There is no way to force messenger logging! The user will always be able to disable it.

Well the user I am talking about is IT handicapped so this should be enough. Thanks for the replies though!