Windows update error code 66a occurs while installing Update for windows System. This is a critical computer error which restricts installing Updates windows system and may cause permanent damage to the system and loss of important files from the system. So it need to fixed urgently. This error sometimes may occur because of driver related issues so use Driver Update software to fix the error. If the error still persists than this error code may have occurred because of corrupted windows registry and invalid entries in windows registry. Download registry repair software which automatically repairs corrupted windows registry and solve the error. For more information, please visit http://www.code66afix.com.