Xiao --
Assuming that you are using Project Server 2007, and assuming that the
Project Server administrator has locked down the default method of tracking
progress in Project Server, then no one can change the method of tracking
progress in any project. If your Project Server administrator has not
locked down the default method of tracking progress, then each PM can open a
project and click Tools - Options - Collaborate, select a new method of
tracking progress, click the OK button, and then republish the project.
Please keep in mind that in-progress tasks will continue to use the previous
method of tracking progress until they are done.
Beyond this, do you really want every PM to decide what method of tracking
progress they want to use? Suppose I am a team member in a number of
projects managed by three different PMs, and each of them uses a different
method of tracking progress. That means I need to know how to track
progress all three ways, which would be challenging, frustrating, and leave
lots of room for errors. Personally, I recommend that your Project Server
administrator specify the default method of tracking progress for all
projects...and LOCK it. Hope this helps.