As I don't truly make any adjustments to the model, the important one to me is the msdb containing all the scripts for jobs. For me, the important one of the three to relocate is the msdb. In the article Hugo has given, I'm not sure the model is needed for relocation of the msdb. http://support.microsoft.com/kb/224071

Curious - can we move MAPI functions from 2000 to 2005 [which uses SMTP]? Wouldn't detach and attach of model and msdb pose a problem for database mail?