Usability is the extent to which a product is effective, efficient, and satisfying in a particular context. Usability assessment can be important for the development of successful products as it evaluates the way the products satisfy the user needs. As emotions are part of cognition, it is reasonable to think they may influence the human interaction with products, affecting the perceived usability. Based on this premise, multiple researchers have proposed models for product appraisal considering objective usability in terms of effectiveness and efficiency and subjective aspects such as the emotion involved. However, these approaches do not include external factors such as skill level, individual preferences and affective states; yet, these external factors may affect the perception of usability. This research work explores the effects of external factors in the perceived usability of products, and specifically focuses on the effect of emotions experienced just before interaction with a product. Data from a preliminary study on the effect of emotional states in perceived usability is presented. The results showed that when positive emotion exists, the perceived usability is significantly higher than the one perceived in the presence of negative emotion.