Is there a way in which we can add rules in the workflow diagram of the work item (Task) so that when the task is closed it will automatically change the completed work to original estimate and remaining work to zero.
I am using the process editor in TFS 2010.
I thought it did this by default - at least for Tasks in the MSF Agile 5.0 process template it does.
Anyway, what you need is a rule on the Transition from Active to Closed to copy some values and and empty the remaining work: