I'm not a lawyer but I'll share what I know.
Actually, copyrights don't apply to domain names because, at the very least, copyrights
apply to certain works like books, articles, paintings, even website design. Rather, you
may be referring to trademarks.
Trademarks, at the very least, apply to words, phrases, and symbols. So trademarks can
apply to domain names because the latter consists of words or phrases.
When registering a domain name, you only have rights to the name itself. No trademarks,
no copyrights, you get those elsewhere.
No one has absolute rights to any word whatsoever, so people can register domain names
using the same words but with different extensions or variations to the name.
Rather, there are limits to registering a name. Trademarks are one such limit every domain
name owner must consider before getting the name if it can be helped.
In your case, here are some questions to consider:
1. How are they using the name?
2. Do you have the time, money, and sincere belief you should get that domain name with
all your might?
As far as I know, .hp is supposed only to refer to products from that famous computer