What is PSSDIAG?
PSSDIAG is a diagnostics utility used to collect profiler trace, perfmon data for SQL Server. PSSDAIG was created to troubleshoot SQL Server 7.0 and 2000 issues. It was evolved and shipped with SQL Server 2005 and beyond. But the shipped product only has a data collector engine called sqldiag.exe. Microsoft Product support continues to maintain a configuration tool that allows engineers to dynamically configure on what to collect. Due to customers' demand, this configuration tool has released under codeplex. please go to Pssdiag/SqlDiag Manager project
If you troubleshoot SQL Server 2000 performance problems, you can continue to use an older version of pssdiag (http://support.microsoft.com/kb/830232