A trade body has warned that the increasing use of hard disks in car infotainment systems means that owners are sometimes leaving sensitive personal data when they sell the car.

The Vehicle Remarketing Association has warned that drivers need to select Delete All before selling the car, or handing it back to the dealer or leasing company – and traders need to make sure that this has been done before selling it on.

There has already been one case of a buyer of a car tracking down the previous owner from information left on the hard disk. Fortunately, this was only to ask him some questions about the car, but the implications are clear. You wouldn't sell your laptop computer on ebay with your personal data still on it, and we all need to get used to the idea that the car is no different.

Some people already take care to put their home address in the sat-nav slightly incorrectly, just in case. After all, no one gets lost 200 metres from their house, so it is no inconvenience. We heard of one case where a car was stolen from the sort of car park where you leave your keys, with the owner's correct home address in the sat-nav. The unfortunate owner not only had a stolen car to deal with – he had a burglary as well.