I try to register IDM on a new computer but it shows a warning message about using it on another computers. What should I do?

If you see a warning message about using IDM on other computers when you try to install it on a new computer, you need to uninstall it from all those computers if it is possible. If you are sure that IDM is not installed or will not be used on any of those computers again you can just ignore this message and continue registration. Otherwise, IDM will detect that it is being used on several computers and your serial number will be blocked.