I have a Window application written in c which makes various record locking requests to a database located on on a Windows server. The code uses _locking calls to do this and has been extremely reliable for over many years of operation. Recently some customers who have upgraded servers from Windows NT to Windows 2000 have seen extreme performance drops. If these customers access the database on an Wndows NT server _locking times are fine. If they access the database on a Window 2000 server the locking times are 10 times slower or worse. I have been unable to reproduce the problems on my own Windows 2000 servers.