recovering a db in sql server 2000

hi,

  a customer of mine has a sql server 2000 in an old server, and for some reasons lost the log file of the db, and now i'm  trying to recover the db.

  i found some links about this problem, like this one:

http://social.msdn.microsoft.com/Forums/en-US/sqldisasterrecovery/thread/2bc8edd5-4c8e-438f-b714-0bf7cc0c6093/

  but even I placed the db in emergency mode, when i try to run the

DBCC REBUILD_LOG 
i obtain the error message that cannot lock the dbase because is in use.
do you know some way to solve this problem?
thanks anyway
  luca