I like computers, parents say commerce, what to do?
It is a tough job to convince parents, but if you have the skills and interest for computer related professions, then you should speak to them about it. It is better to choose something that you have interest and skills to match.
You can speak to them or try and speak to some elders in your family, like an elder brother/sister or uncle/aunt etc., You may also take help of your teachers to talk to them.
Alternatively, you may consult your teachers and tell them to suggest a good aptitude test at a reputed career counselling centre near you. An aptitude test would reveal where your skills and interest lies, and may be your parents would be convinced by the report the centre provides.