The error message is perfectly clear - there is no application installed on the computer where your application is running which can open an
.rpt
file.
And it's unlikely that you'd want to open the file anyway. That would simply open the Crystal Reports designer, whereas you probably want to bind the report to some data and display the output.
To do that, you'll need to write some code. Google has lots of examples to help you. Eg:
How to Load and Display Crystal Reports in VB.NET[
^]