Question : Configuration option 'Agent XPs' changed from 1 to 0. Run the RECONFIGURE statement to install.

I have just upgraded to SQL Server 2005 from SQL Server 2000.In Microsoft SQL Server Management Studio, when I click on the SQL Server Agent log, I receive the following error. Configuration option 'Agent XPs' changed from 1 to 0. Run the RECONFIGURE statement to install.

Answer : Configuration option 'Agent XPs' changed from 1 to 0. Run the RECONFIGURE statement to install.

If you can't enable the Agent through the GUI, something may have gotten messed up elsewhere.  Try the steps listed here:
http://www.rprabhala.com/Dasblogce/blog/CommentView,guid,ee1c2143-5e5a-46de-9685-f096a674121b.aspx