To install registry keys based upon a file on the destination computer add a system search that searches for a file on the destination computer from Installation Expert's System Search.
If the file is found, a property you specify in the System Search action will be set, if it is not found, the property will be empty. Use this property as a condition on the component that contains the registry key or file that is getting installed based on the search.
If the file is not found, the property will not get set. If the property is empty, the registry key or files will not be installed because the component is conditionalized to check the property from the System Search.
If the file is found on the destination computer, the component will be installed.