account to add a machine in domain in windows2008r2

Dear all

   I have windows 2008r2 DC. Rightnow we are 3 members handling the administrator account which is insecured so

  I my requirement is one should handle administrative account and others should not have but they should have permission to add new machines to domain and also to backup the folders resides in D drive.

  And my another scenario is I have hidden folders which are all used for confidential purpose, The person who is taking the backup should not see the hiddenfolders in D drive and should not be accessible. kindly help me to resolve this issue.

Regards

chandrasekar.M

M.chandrasekar