Microsoft Has Encountered An Error

running Windows XP home edition and every time she goes to press the internet explorer icon on her desktop it will load the home page ok then when you try to surk the net she gets the message that microsoft has encounted aan error and then it asks if you want to send the report or not. If you click either send or dot not send report it boots you off the net and goes back to the desktop. Also she cannot even do internet banking, because every time you try to you get the same message. We think she may have gotten a virus, but we don't know because norton doesn't find anything wrong.