How to recover crashed Exchange Server 2003 ?

I have a Ms Exchange Server 2003, and it is showing an error in the database schema.
Exchange Server has crashed due to what reason, is what really surprises me. I am not able to make it up and leave.
I have a backup of last week but not yesterday. If I install a fresh server from the beginning,
I have to do all the exercise and only install last weeks mails which I really don't want to do.
How to recover crashed database of Ms Exchange Server 2003 ?
