I encountered the above error message and code when I try to connect to my Windows Live Messenger on my Windows 7 office’s workstation. When I clicked on the SIGN IN button in Windows Live Messenger, an error message just keep popping up that Windows Live Messenger service is not available.
Clicking on the round MORE DETAIL button show an error code, 80040200. Initially I thought the firewall was blocking Windows Live Messenger services. But running thru the log, I did not notice any unusual deny rule in the log file that indicate Windows Live Messenger ports or service has been blocked by the firewall.
In frustration I exited Windows Live Messenger program and went to task manager to ensure that msnmsgr.exe is not running and end it process and open Windows Live Messenger again. And viola! Finally I can sign in to Windows Live Messenger.
Chiawy's Blog 
why does it tell me it is unavailable
tells me its unavailable