Skitttles is right on the money, if the signage says Laptops it does not apply to a desktop they are DIFFERENT. The other point Pat needs to discuss with Management is the statement made by the Best Buy Sales Rep, if the Rep in fact said "return in 14 days for a FULL refund" (Full Refund does NOT mean Refund less restocking fee), Best Buy is very likely required to honor that statement, (I am not up on every state consumer protection law, but that is common in most states and provinces in Canada, the wording varies but the principal is the same the Company is responsible for commitments made by associates used to entice consumers to make a purchase).
I had a dispute with a Canadian Big Box store (this store is owned by "Best Buy") a few years ago, along the same line, I purchased several items as Xmas gifts for the Family - doing the guy thing shopping on Xmas eve. The problem for me was the Boxing Day Sale, 3 of the items went on sale 4 days later, at 20% of what I paid, you know I was please to see that. The store policy was if the item went on sale within 7 days you got a refund - that seemed reasonable, I go to the counter and show my receipt asking about the "Price Protection" and was told "no returns or refunds are allowed until after Jan 2nd due to the madness of the post Xmas sale, however I could simply buy the items again at the new price and return the first purchases for a full refund, or come back for the "Price Protection" after Jan 2nd, seemed reasonable! I decided I did not want to buy over again so I made a couple of other purchases, went home happy, and returned after Jan 2nd, Oops sorry sir you are past the 7 day limit... now I am NOT happy, I asked how I could have received the refund when they would not allow it during the sale and was told sorry that is the policy, I asked to speak to a manager and was told to wait, after 20 minutes I asked again and was told the Manager was on break and would not be back for another half hour (nice break). I left a very UNsatsified customer! I decided not to give up, and went to the Contact Us link on the company site, after several messages back and forth I was getting no where, finally a message to the BBB, and the "Manager on Break" appears via eMail and asks me to come see him in the store, the BBB pointed out the conflict and the consumer protection laws, I expect he knew he had little choice but to satsify my complaint. I do give him credit, he not only took care of me, he turned my opinion around about his employer. He fully agreed the policy around Xmas returns caused problems with time limits and he also agreed he as a manager had to take responsibility for the commitments made by his staff, if they were mistaken he needed to provide better education of policy and how it is applied, and if they were saying things that were wrong (as in lieing to make a sale) there was a larger problem to deal with.
Bottom line, don't stop at a refusal or decision of a Sales Associate, go to a manager, and point out (in a reasonable way) your concern, they are not always easy to deal with, but most Managers understand customer complaints are an opportunity to build a stronger customer relationship, and they will do their best to help.
In my case, I was more than satsified, and since that time I have spent several thousand dollars at that very store, and I get a smile and a nod from the manager every time we see each other, he knows he did right by me and his store is benifiting from that decision.
Best of luck to Pat on this one!