I checked the link Naomi sent me and it takes to this link
http://msdn.microsoft.com/en-us/library/ms345295(SQL.90).aspx
and it says in some part

With Database Engine selected on the Registered Servers toolbar, right-click the Database Engine node in the tree, and then click Update Local Server Registration. All instances of the Database Engine installed on the computer are displayed. This includes instances of SQL Server 2000. Management Studio can connect and manage instances of SQL Server 2000 and also SQL Server 2005.

When i click "Update Local Server Registration" no instances of Database Engine were displayed
Could anybody have any ideas to help me
Thank you