We recently had a client who had accidentally deleted their BESAdmin account within Active Directory and needed to get it back.  We found this document to help us recreate the user account.  The one part of this document that needed to be adjusted in this case was on the step where we are instructed to do a registry export while being logged in as the old user, we had to log in as an administrator and find the old BESAdmin’s key within HKEY_Users and export it from there.  You will be able to find the BESAdmin’s key easily, as it is the only one that will have the Research In Motion key.  Additionally, once the export is complete, we had to edit the export before re-importing it by adjusting all of the entries indicating “HKEY_USER”, replacing them with “HKEY_CURRENT_USER”.

http://www.blackberry.com/btsc/viewContent.do?externalId=KB04293&sliceId=1