I thought the Disputes Tribunal was for resolving disputes. Doesn't seem to me that there is a dispute here - yet. OP ought to be given an opportunity to resolve and if not satisfactory to purchaser then dispute triggered.
I'm surprised there are so many people telling the OP to tell the buyer tough luck. The OP sold the laptop through an "in Trade" account which means the CGA does apply. If the OP was a big box retailer I guarantee most people will be on the side of the buyer.
I would suggest to find out what the problem is with the laptop and get it sorted, hopefully it will be a quick and easy fix.
I haven't actually seen the fault - I received the notification of the dispute from trademe - then I emailed the guy to say hey it's 10 months old sorry can't help - then I received a further email from trademe asking me to resolve the issue with the buyer.
So has the buyer actually replied to you yet?
Lots of advice in this thread; to offer some money back, to tell the buyer to go jump, any disputes tribunal speculation, appears moot to me until you've had a chance to assess what's actually wrong with it and your deciding whether you will (help) rectify it.
"I have noticed even people who claim everything is predestined, and that we can do nothing to change it, look before they cross the road." - Stephen Hawking
So I've decided just to stand my original ground.
When I listed it I did say it was a 2015 model in good condition. So, I feel that a second hand laptop that pushing 3 years old could go either way in a dispute. The mixed opinions here kinda confirmed my thinking that I wasn't being too unreasonable.
So far the buyer only seems to want to communicate with TradeMe who just forward emails.
If he does decide to take it further I think I'd have a reasonable case -
In the end if it doesn't go in my favour I haven't really lost anything eg - it won't cost me any more to refund it anyway and he's got to lodge the claim and wait for the hearing.
It's also an ultrabook so the design makes most repairs uneconomical so barring user error there is probably not a lot I could do to remedy the situation apart from 'refund' anyway.
I'd tell him to take it to a repair place to get assessed. If cost of repair is >$500 then offer a partial refund (maybe $300 as someone suggested). If he says no tell him to shove it.
If it is an Ultrabook I would try the manufacturer to check the warranty status. Many top end laptops will come with a three year manufacturer warranty. Usually you can just type the serial number in to the site and it will tell you.