Today I found defective pixels on my laptop screen. Pixels are black, that is, they do not glow on any color of the screen. Please tell me what to do with it? Is this question solved under warranty on the laptop?
If the system is less than 30 days from shipment, contact Dell to have it replaced under the 30-day satisfaction guarantee.
Beyond 30 days but in warranty, see here; there need to be six or more dark pixels before they'll replace the screen.
I bought my laptop in Costco. They have a 90 day return guarantee. Can I change this laptop in to a new one without sending it to Dell?
That's up to Costco -- you'll have to ask them.