I have received a couple of questions regarding HP guarantees. You need to know that HP is offering a 1 year guarantee in general worldwide, but it is important to know that the guarantee applies only for the region you have bought the calculator. The world is divided in three regions: Americas, EAME (Europe, Africa and Middle East) and Asia.
This is intended to avoid "grey imports" whereby a company imports calculators from a cheaper place, in some cases circunventing the import duties. It is a nuisance, but this is the way it works!
Moreover, in EAME we have different versions for the groups of countries we have in Europe. Typically there is an English-French version, a German-Italian-French-Dutch, a Scandinavian version and a Portuguese-Spanish version. Primes come in an international version - again different from what is supplied in the Americas.
Typically, when there is a problem with your HP calculator, if it is a new model, there are basically no parts to repair. If it is less than one year since you bought it, you can call HP's support telephone. They will go with you through a number of questions, but most likely at the end they will agree to send a new calculator to you. This calculator will be wrapped in "bubblewrap", without manuals, case or accessories. (In fact, some sellers in Ebay are just selling a batch of these HP35s replacements, as new calculators. I think HP should do something about it). It will arrive very soon, typically in two-three days. and you'll not be required to return the defective one, in most cases.
You can also try repairing it yourself. Some models are easier than others, and here internet is your help. However, all calculator aficionados are waiting for a book on HP calculator repair by Geoff Quickfall. He has put all his experience in that book, that he's now proofreading. I look forward to get a copy, and you'll all know when it happens.
If your calculator is old, then a repair is a definite possibility. Voyagers, HP41c, HP65/67/92/97, etc.: most of them can be repaired, and it will continue to be your trusty calculator. To do that, you can call us in Europe (we have a partner that takes pride in his repairs, and treats them as a challenge.