Well, if the buyer did not make the purchase via eBay (clicking Buy it Now, Best Offer or winning an auction) and you get that kind of email then yes, it is a scam attempt. If the buyer did commit to buy it via eBay then you can check eBay and PayPal, if there's no mention about payment and "OK to ship" etc. then no payment has been received. Still, the item you are selling is very attractive to scammers, even if you do get payment and send the laptop, things might not end well with PayPal. You basically give 6 months of warranty for that laptop when you sell it.