I found this information in this page:
When SQL Server 2005 Express ships, it will be the best database you can use for many scenarios. While you can't use it for production code today, now is the time to start ensuring that you will be able to use this excellent, free database when it ships. If
you're currently using MSDE, migrating to SQL Server 2005 Express will be trivial. You can simply take the existing .mdf file for your MSDE database, ship the file with your application, and connect to the file by putting the file path in the connection string.
It's likely that no other changes will be needed. However, you may want to make some changes (for example, using MARS instead of multiple connections) to streamline your code.
Forgive my poor English, I want to confirm one thing:
Could I use SQL Server 2005 Express edition in Production environment?
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