Chatting online is a little bit like chatting to a stranger at the bar or at the park. There is no way for sure to know if that person is telling you the truth. Just as you should not give your real name and phone number to a stranger; you should not reveal your personal information on-line either. Do you know for sure that it's your best friend sitting in front of the other computer, or could it be their husband or their sister?
Use only generic information that cannot be used to identify you. Often chat programs will allow you to set up a "profile." This information is always optional and in most cases it is more appropriate to leave it completely blank. Use a fake name and create a "disposable" email account when chatting on MSN. You may even want to hide your gender when you are chatting on-line.
Most "chat" and instant messaging programs have a feature which automatically logs all conversations. If you think your home computer might be monitored by someone else in the house be sure to turn this feature OFF. In MSN your message history is available from: TOOLS -> OPTIONS -> MESSAGES TAB...... then at the bottom... Message History. Be sure to clear this history when you are done your conversation.