1.) Close Messenger. Go into Task Manager and ensure that the “msnmsgr.exe” process
is not there. If it is, kill the process.
2.) Navigate to C:\Users\<YourUserName>\AppData\Local\Microsoft\Windows Live
Contacts and delete the entire contents of the folder.
3.) Restart Windows Live Messenger. Voila!
There is another issue I found where the standalone installer for Messenger fails
with a message like “could not open key…”. One fix for this is to navigate to
the C:\Program Files\Windows Live\Messenger folder and DELETE the msnmsgr.exe
executable if it is there.
The new "Windows Live Installer" creates problems for many users. Often
it will try to install selected programs, get to the very end, and then proceed
to "Roll back" everything.
The worst part is that the wlsetup-all.exe, which has all the installation files,
cannot be uncompressed, unpacked or extracted into a separate .MSI installer
for each individual software.
Here is how to get the "Standalone" after you have run Windows Live Installer:
Open Windows Explorer, and set it to Show hidden files and folders and show protected operating system files (uncheck the tick for Hide protected operating system files) in the View tab of Folder Options.
Browse to \Program Files\Common Files\Windows Live\.cache\ folder.
Search the subfolders for "Messenger.msi". There may be several, you want
the latest one.
You can now copy this to a convenient location, and install Messenger with it. You
may also need to find and install "Contacts.msi" to avoid errors.