You do the conversion under Tools | Database Utilities.
The point is that it locks the design of forms, reports and modules so that
your users cannot change them.

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Doug Steele, Microsoft Access MVP
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> how to convert the extension .mdb to .mde and what's the use of this?
Make sure that you keep the somewhere that is safe. If you lose it, you will
not be able to convert the mde back to an mdb.
Dale

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> how to convert the extension .mdb to .mde and what's the use of this?