If the company go bankrupt the shares will be written down to zero.No they can not go to 0 unless the company have no value. It is impossible to give advice since I do not know what company you have shares in. I hope it is not a building company.
How is the future for the company, have you read any guiding from the management? Have you read the annual report? Do you believe the company have a future, if they do you sit. You can calculate the value of your shares by reading the annual report. Can you afford to take the loss? They can be hit with the present bear marked and rally up when the market turnes. Share prices are based on present and future possible earnings. You chould have a stop loss strategy, sell if the price drop e.g. 10 % from the price you bought them.
This could be a good site for you. Found it on google.
http://stocks.about.com/