I used to run Windows XP with Office 2003, and when users tried to open a document twice from a network share, the second user gets the locked for editing message However on Windows 7 and Office 2010, users no longer get this message and are free to edit the document regardless of who has it open Is there a setting in Office 2010 to enable this?

If you're not getting that prompt, it suggests a fault with your network. Either that or the users are opening different copies of the document. It is the network operating system that manages file locks, not Word.

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]