Can not remove Norton Antibot

I just recently upgraded from Norton 360 V2.0 to Norton 360 V4.0 via a CD which I bought.

 

When trying to install, I get error message:

 

"Norton AntiBot was found on your computer and has to be uninstalled before installing Norton 360..."

 

When I try to remove Antibot via "Control Panel"/"Add or remove programs" I get error message:

 

"file invisibleutility.exe is not marked for installation"

 

After clicking ok, I get additional error message: "Fatal error during installation" and Antibot is not removed.

 

Installing Antibot new and uninstalling again does also not work.

 

I understand there should be a solution, but unfortunately it's reported offline and not in the forum.

 

I need urgent help. Who knows the trick??

 

Appreciate your help greatly in advance