If you want to go back in time before you installed the latest edition of Windows Live Messenger to need to use "System Restore". To use system restore, go to:-
Start
All Programs
Accessories
System Tools
System Restore. then click on it.
Check that "Restore my computer to an earlier time" is highlighted, then Next.
You will now be presented with a calendar with some of the dates in BOLD. These are system restore points. Choose one that is earlier than when you installed Messenger, by clicking on it , then select "Next". Your PC should then restore itself to the condition it was in before that time. Your existing emails will not be affected nor any documents you have created. Any software installed since that date will need re-installing.