Files that contain the .plsk file extension are normally used by the Windows Live Messenger application.
Windows Live Messenger is an instant messaging software application that enables users to chat online in "real time" with their Windows Live contacts. The PLSK files that are used by this program contain custom "skins" that can be used with the Windows Live Messenger program. These "skins" allow a user to change the look and feel of the application's interface.
In order to use PLSK file skins with the Windows Live Messenger program, a user must have the Messenger Plus! add-on installed on the Windows Live Messenger application.
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