First thing, give the retailer a chance to put things right.
IMO 15 months is an unacceptably short time for a laptop. You may be requested to partpay some of the replacement parts, which is fair enough seeing you'll be getting new parts. Many retailers are fair minded people.
Next option would be to find out from your local consumer's right representation what they would consider an acceptable time for a laptop.
Notwithstanding any guarantee, you have the right to expect a purchased item to last for a certain period without faults, this ofcourse is different for each item and excludes fair wear and tear. Be reasonable and don't expect a new free replacement after 15 months.
Good luck.