HI vamsi, When you say ADC does that mean Acvite directory Connector. If yes there is not need of ADC when u dont have exchange 5.5. However, if you are refering to system state backup of Active Directory..then below is the answere ...First thing first... Installing Exchange on a Domain controller is a BIG NO NO... Reson..Exchange depends a lot on Active directory. Whenever the SA services starts it looks for all the domain controller in the domain and keeps a list of it and one server is elected as the configuration DC. When one domain controller goes down its contact the other DC/GC..which is called as Inteligent Failover.. This will not happen if you install Exchange on a DC/GC. Coming back to your question..In your case if the Domain controller fails then you get the server back and ran the exchange setup with the /disasterrecovery switch assuming that u have another DC and all the information has been replicated to the other dC. This will get the Exchange org and site information frm the AD and install exchange realted files to the local system ..after this restore from backup. If you do not have a backup but u r able to retrive the database files from the crashed system then u can try repairing it using eseutil /p. Why take a chance, ackup ur data daily. Please visit the Web site to download ur copy of disaster recovery guide. http://www.microsoft.com/downloads/details.aspx?FamilyID=A58F49C5-1190-4FBF-AEDE-007A8F366B0E&displaylang=en add info.. http://www.microsoft.com/technet/prodtechnol/exchange/2003/library/default.mspx However, if this is not the right information u r looking for then please resend ur message with a scenario and we will be able to help u better. Manoj " Jack of all trades, master of the moment"