If you ever package users from one Sitecore instance to another you will find that upon install the users are disabled and the passwords need to be reset.

What if you were moving them from one version to another and need to keep the same passwords?

Fear not, just run this SQL script. It will update the passwords of all matching usernames to the original passwords, and enable the accounts. The databases must be on the same instance.

/******

 SELECT Upgraded Core DB in SQL Studio.

 In script below, Replace Old_Core with name of old DB

 First run the SELECT only to see what it's going to do, then run the update script.

 ******/
SELECT TOP 1000
      m.[UserId],
      om.userid,
      m.[Password],
      om.password,
      m.[PasswordSalt],
      om.passwordsalt,
      u.username,
     ou.username,
      m.comment,
     m.islockedout,
     om.islockedout,
     m.isapproved,
     om.isapproved
  FROM [aspnet_Membership] m
  inner join [aspnet_Users] u ON m.UserID = u.UserID
  inner join Old_Core.dbo.aspnet_Users ou ON ou.username = u.username
  inner join Old_Core.dbo.aspnet_Membership om ON ou.userid = om.userid

   UPDATE [aspnet_Membership]
  SET
  --comment = ou.username,    -- TEST!
  Password = om.Password,
  PasswordSalt = om.PasswordSalt,
  IsLockedOut = om.IsLockedOut,
  IsApproved = om.IsApproved
  FROM [aspnet_Membership] m
  inner join [aspnet_Users] u ON m.UserID = u.UserID
  inner join Old_Core.dbo.aspnet_Users ou ON ou.username = u.username
  inner join Old_Core.dbo.aspnet_Membership om ON ou.userid = om.userid