Computers have become an integral part of every field including business. Are there any courses by top universities, that provides courses on diagnosing computer for the business students?
I doubt there are any courses which help you diagnose a computational device. There are loads of courses on Coursera or the likes which may aid your understanding of certain fundamentals. Major colleges do not aid your understanding of conventional computers - they focus on the process of engineering of core aspects of a computational device or environment.
You might want to explore:
https://www.coursera.org/courses?languages=en
https://www.edx.org/course?search_query=computing
Then there is udacity (google it) and so on. FOC, so it should aid your understanding of the fundamentals. Pretty useful but, my own experience (as a business student first/computing professional later), I would probably advise you to self-explore more.