Here you'll see a step-by-step guide.
Exit Windows Live Messenger or MSN
Messenger completely (Right click on
WLM button/icon on Taskbar and select
Exit). Go to Start Menu, locate the
Windows Live Messenger shortcut. Tip:
It’s also possible to deal directly
with the actual WLM program,
msnmgsr.exe located in
%ProgramFiles%\Windows Live\Messenger\
folder.
Right click on the Windows Live
Messenger shortcut or executable, and
select Properties.
Go to Compatibility tab. Tick the
check box for Run this program in
compatibility mode for under
“Compatibility Mode”, and then select
Windows Vista from the drop down list.
Click OK. Run Windows Live Messenger