Logitech - Dell - HP

You need a lot more than just a serial number and a convincing story now, maybe 4 years ago that would work, but tech companies especially are pretty reluctant to give out more than $100 of stuff without any physical proof in front of them. Easiest way to get dell,hp or Logitech for free is making a burner amazon account, ordering a product, requesting a refund, then getting the same item again and selling the 2nd one.