Have you encounter this problem? After installing the “latest” Windows Live Messenger 2009 but wonder why always getting the error which you cannot sign in? (Unable to sign into Windows Live Messenger – Error 80004005)
With all the frustrations, thought something went wrong with the Internet connection, wrong username / password entered or even WLM’s server is down. You even click on the link provided with the error message to search through Microsoft’s Knowledge Base, followed the instructions given, yet still scratching your head with the same errors.
Okay, in the end, you gave up and wanted to uninstall the software. Wait, where’s the uninstaller? Searching through the Start menu, you even went to C:\Program Files\Windows Live\Messenger to search for the uninstall.exe file. What? Cannot find it?
Here’s a trick I found from this useful blog:
How to uninstall Windows Live Messenger 2009 using RUN
To uninstall Windows Live Messenger, click START, then Run if using Windows XP [operating system]
then [type/copy] the following and press Enter: [it works 100%]
msiexec /x {0AAA9C97-74D4-47CE-B089-0B147EF3553C}You will notice that the Windows Live will be removed from your “Start” > “All Programs” list.
Source: http://ayumilove.wordpress.com/2009/03/14/how-to-install-remove-windows-live-messenger-2009/ by ayumilove
Thanks for the tricks from this blog, finally I can get this little devil removed.

