If the airbag light just came on, it usually means that there is a problem with the airbag system, so resetting the light isn't going to fix the problem. I would start by diagnosing the airbag system and figuring out and fixing the problem before resetting the light. If your car has a worn seatbelt (given the age) that might be the cause of the problem, rather than the airbag itself, since the restraint system has to be in working order for the airbags to work properly.