Help me any system admins please please its very urgent for me?

i am having serve 2000 of installed with dhcp and 25 client systems. if i want to format my server and re-install and i want the same permissions and settings which are at present what should i do before and after format and installation. what i should do with client systems. and how to take the backup of outlook and tally and other softwares in server and clients systems please help me with all details .