There is only one file type that uses the .NICK extension:
Outlook 2000 Nickname File
Stores a nickname for an Outlook user, which is linked to a complete user profile; enables a user to enter a string of characters and assign it as a nickname for an e-mail address.
Outlook 2000 and earlier uses NICK files. Outlook 2002 and later uses .NK2 files.
|Microsoft Outlook 2000 or earlier|
Updated: September 2, 2008