OK I have my suspicions that a fault that we are experincing is being caused by a particular DLL. So what I need to do is prove it. I think I know which dll it is but I want to be able to track the server performance when the DLL is called. I can see via Dependancy walker that it is being used, but as to the frequency and its correlation to tthe given problem I don't know of a tool that can accomplish this task. Does anyone else out there know. What I would also like to know is how Microsoft prove that a particular DLL is causing a problem. Mark Shevill IMG Messaging Technical Lead Shell Information Technology International Limited Rowlandsway, Wythenshawe, Manchester M22 5SB, United Kingdom Tel: +44 161 435 8709 Fax: +44 161 933 3502 Other Tel: +44 7932 625510 Email: Mark.Shevill@xxxxxxxxx Internet: http://www.shell.com <http://www.shell.com/>