The SharePoint test data load tool (WSSDW.exe) is a performance testing tool that populates data for testing deployments of Office SharePoint Server 2007. The SharePoint test data load tool is available as a command-line executable program that accepts an XML configuration file that specifies the objects to be populated. The SharePoint test data load application calls a Microsoft .NET assembly (WSSDWLib.dll). WSSDWLib.dll can also be called from other applications.
This is a must use tool for all deployments over 50 users.
Here is more -- http://technet2.microsoft.com/Office/en-us/library/301ed832-95da-4251-b266-7be6288f7ea01033.mspx?mfr=true
