If you explicitly stated that you wanted a laptop that would work with your exisitng scanner and printer, gave details of the models and were told they would work with the laptop you bought, you bought the laptop in reliance on the statement made by the salesman. If these comments are erroneous, you are entitled to return the item as it is not fit for the purpose you specified. However you may find it difficult to prove this and you will be asked to justify why it has taken you 6 months to return the item - I think this is too long to be considered reasonable under these circumstances I'm afraid.