I'd just give them the shares back and even the laptop too if can afford to. Just start from a blank slate and don't risk the chance of something biting you in

I'd just give them the shares back and even the laptop too if can afford to. Just start from a blank slate and don't risk the chance of something biting you in the future. The shares don't mean anything to you.. if you're leaving it probably means you're almost sure that startup won't make it big.