Is my business allowed to use the same name as a nationally known business in a different industry? -

Say I want to name my business Jupiter Computer Repair but there s already a national brand of shampoo called Jupiter. Is it legal for me to use the name Jupiter since we re in completely different industries?

Yes. And I doubt the name Jupiter is (and I doubt can be) trademarked. And no one would confuse your business with a shampoo company. If they do, well, they are just stoooopid.