Email Accounts and recovering messages

I am also responsible for a small network system. We use Windows NT 4.0 and Exchange 5.5 on one server. I was on vacation last week and my assistant updated (without checking that it had been done before) for the worm of the week last week. Needless to say the system refused to come up afterthat, so he rebuilt the entire system and the email. We also kept the exchange on a differant partition, and all the data is there. So how to I migrate this information to the new exchange system? All the data is the same (sever name, etc).