rebuilding the database creates a fresh master, and would not retain the links to teh databases that were there previously.
fortunately for you, the MDF/LDF's will still be in place onthe drives, so you just have to attach them; browse for the mdf files and attatch them one by one.
also, note that all your logins , any linked servers, and any users/roles that used to live in master would be gone and you need to recreate them.
also, changing the collation of the master database does not auto-magically change the collation for databases, or the collation of each varchar/char/nvarchar/nchar/text colaltion in any of those databases;
those have to be fixed individually.
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