from my point of view, the seller cannot bear all the responsibility.
1st of all, from wat i see is, the seller is polite and willing to suggest ways to solve the problem.
probably he thinks the pc has not enough power for the usb port.
high end sure got power? i dono, but buyer say test at a lot computer liao, still cannot work.
seller can also remote control the buyer's pc and try it out. i think if it really doesnt work, then the seller oso confirm cannot work, coz at least he tried remote control edi. no more excuse.

well, best now is meet up and try the player on the spot,
OR
refund but buyer bear shipping charge, that's wat i think is fair.

hanyalah dua sen saya.