Nadia --
In the future, please tell us what version of Project Server you are using.
2002, 2003, or 2007? If you are using 2002 or 2003, you can navigate to the
Resource Center page in PWA, click the View Resource Assignments link in the
sidepane, and create the report you wish to see. The View Resource
Assignments page will show you all tasks in all projects assigned to the
resource(s) you select for the report. Hope this helps.