I passed by this experience after the deletion of a DHCP superscope where the Superscope reverts back after the DHCP server is rebooted or after the restart of the DHCP service. To properly remove a DHCP Superscope, you can perform any of the following methods:
- How DHCP Technology Works: http://technet.microsoft.com/en-us/library/cc780760(WS.10).aspx
- DHCP Superscopes: http://technet.microsoft.com/en-us/library/cc757614%28v=WS.10%29.aspx