[WhatDoYouThink!]

Your seller means manufacturer?
Your warranty is from manufacturer not from seller.
Never remove the seal. Your warranty will be void.

How do put into word?
A person who knows computer will build his own pc. He won’t buy off the rack pc with limited expansion capability. It is actually an insult to buy prebuilt desktop pc from the rack.

Within the first few days usually bring back to the sellers.

But how do you know which parts or componets which are faulty? Aiya pay a bit more let them assemble better lah.