Run Multiple Instances of Messenger

To be able to run multiple instances of messenger (Messenger多账户登陆) is always an appealing function for messenger users, in the past users would use third-party plug-ins such as Messenger Plus! or MSN Shell to get additional features and functions, however, now the new messenger (version 9.0+) added native support for that, although it was not officially integrated, there is a trick to do that.
I remembered to realize that function when I first used Live Messenger 9.0 without doing anything, however, after a re-installation of my OS, and messenger of course, I could not use the feature anymore, I inspected the installation pack, and the sign-in assistant is there, why?
After several searches through Google, I found following hack on the registry will get the function back:
Open registry editor, and navigate to
"HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Live\Messenger", right-click on Messenger and create a new dWord, name it as "MultipleInstances", set its value to 1.

Close registry editor, and now you can run as many messenger as you like, as is shown in snapshot below:
Well, it's done, but one problem I am not sure is whether it has something to do with sign-in assistant, which is described as to be used for linking multiple accounts.