Many times you want to run multiple instances of Windows Live Messenger (Polygamy) , either just to test or to make use of your multiple Live IDs at the same time. Earlier you  might have done this using third party add-on or a patch. Now those are not needed, as a registry tweak will enable  you to run multiple instances. This nice tip has been provided by LiveSide which was shared to by Microsoft’s John Weisenfeld.

Let us see how this is done. As it involves Registry, take a back up of the same.

- Start Regedit.

- Navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Live\Messenger

- Right click Messenger and create a new DWORD called MultipleInstances.

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- Right click on the newly added DWORD and choose Modify

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- Set the Value data to 1, Press OK.

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- Close Regedit.That’s all.

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poly6 Now you can sign-in to Windows Live Messenger with different Live IDs at the same time thus running multiple instances. You can’t login with the same Live ID more than once else you will get an Error. If you haven’t yet installed the new Windows Live Messenger, get it from http://download.live.com/messenger