If I have to reformat a Server 2008 system, how do I get all the users information (usernames and passwords) copied to the rebuilt system?
User's Information: Backup it up with wbadmin at an elevated command prompt or just copy / paste it to another source.
Usernames: If it's in a domain, open ADUC, create a query for usernames and export the information to a text file. If it's in a workgroup, open the Local Users and Groups MMC, right lick the "Users" folder and select "Export list"
User's Passwords: From a practical standpoint, you can't... unless you want to try to crack the NTLM hashes.