Do you get any error code along with the error message?
Do you have Microsoft Visual Studio installed on your computer?
You may perform clean boot and then try to install Windows Live Messenger. Clean boot will
start Windows7 by using a minimal set of drivers and startup programs and helps to eliminate software conflicts.
Note: Please ensure that the computer is set to start as usual by following the step 7 from the article: How to troubleshoot a problem by performing a clean boot in Windows Vista or in Windows7: http://support.microsoft.com/kb/929135
Hope the information helps. Please post back and let us know.
Microsoft Answers Support Engineer
Visit our Microsoft Answers Feedback Forum and let us know what you think.