Hello to all and thanks for your answers.
The time you discussed we found a perfect solution and it will work for 99.9% of our Windows systems.
As I described, we wanted to install The Robot 100% automatically. Without setting something in hosts file, without adding something etc.
So, the computers will have only one network card so ... we build a script that installs an old version of Robot (7.70, it has /verysilent key), runs ipconfig, gets ip address of computer and then edits robot.cfg file; and starts the Nimsoft service. Everything is automatically and via group policy script.
The next thing I need to add some probes automatically to the new client but it seems that it us another story
Thanks for all for your help!