Windows Instant Messenger could be legitimate Windows OS process. Windows Instant Messenger comes with some versions of Windows and is used chat online with friends/family. Windows Instant Messenger is not to be confused (although similar) with Microsoft Network (MSN) Instant Messenger. Windows Instant Messenger supports Application Program Interfaces (API), and enables ability to connect to intranets: Communication Service(audio available here) and Microsoft Exchange Instant Messaging. Application Program Interface (API) -platform for building software applications that enable software developers to access various system resources/features without writing hardware-specific code. CAUTION: Various trojan/worm/spyware overwrite or create a file by this name.