Sometime happen (hopefully) that you have to dismiss old and not supported Operating System (aka Windows 2003) and during the process you need to move the DHCP server.
If both server have the same language, you will not face any problem but, if source and target server are in different languages (sometime, for no good reasons, IT technicians install the OS in their own language instead of English), the import process will fail to match the correspondent DHCP class.
The error raise is: Error while importing class “Default BOOTP Class”. This class conflicts with the existing class “Default BOOTP Class”.
Here the manual workaround to solve this.