(from Revit OpEd)
CHANGING USERNAME AFFECTS NEW USERS
Once you have manually overwritten the user name it will no longer automatically be whatever the Windows login name is. If there is only one person that ever uses that particular computer then this probably doesn't matter, but if it does matter to someone, this is how I've found to fix this behavior (hope the indenting shows up correctly):
Close Revit.
Locate the Revit.ini file on the workstation.
For 2011 the default location is: C:\Program Files\Autodesk\\Program.
When the username is overridden the following 2 lines are added to the Revit.ini file:
[Partitions] Username=X
You can search the file for this; the X above designates the specific username.
Remove both lines from the Revit.ini and save. When the next user, and subsequent users log onto the workstation Revit will pull the Windows username.
USE OFFENDERS LOCAL FILE
If you have a co-worker that didn't relinquish everything before leaving the office the safest approach is to open their Local File on their PC and Sync for them. This means if they didn't Sync with Central their work will be added to the central file.
This means you have to be able to log onto their PC as yourself
Change the Revit username to theirs if isn't already
Then you have to know where their Local File is, open it and SwC
Reset their Username
Close Revit
Log off their PC.
Let them know what you did! They'll probably see your log-on-name when they return and wonder.
DO IT IN THE CENTRAL FILE
Take the following steps only if you are certain you are the only one using the Central file.
Open Revit (if it isn't already, don't open any files yet)
Close your own Local File (if Revit is already open)
Change your Username to match the missing person
Open the Central File (don't check the local file option)
You are now working in the Central File (most reliable if no other users are working in Local Files, if they Synchronize with Central while you are doing this Revit may insist on having you create a local file before being able to Synchronize with Central)
Synchronize with Central - relinquish all worksets
If there are other users involved - change your Username to match another
Repeat the process (again, other users might force you into a Local File, most reliable if no other users are actively working in the project)
CREATE NEW CENTRAL FILE
This method replaces the existing central file with a new one. Note that if you use the same name all backups will be deleted.
Make an archive backup before using this method.
Open the Central file - Check the Detach from Central option
Save the file - provide a new name when prompted
You now have a new central file
Synchronize with Central - relinquish all worksets
Close the file
Have users create a new Local File based on this new Central File to begin work