If you would like to use the Performance Dashboard 2005 on SQL Server 2008 you will have to make the following change in the usp_Main_GetSessionInfo stored procedure.

Change the line:

sum(convert(bigint, datediff(ms, login_time, getdate()))) - sum(convert(bigint, s.total_elapsed_time)) as idle_connection_time,

to

sum(convert(bigint, CAST ( DATEDIFF ( minute, login_time, getdate()) AS BIGINT)*60000 + DATEDIFF ( millisecond, DATEADD ( minute, DATEDIFF ( minute, login_time, getdate() ), login_time ),getdate() ))) - sum(convert(bigint, s.total_elapsed_time)) as idle_connection_time,