Notebook Hardware and Upgrade Questions

I purchased a laptop from an electronics store a month ago... The latop was a Certifed Refurbished model and I noticed there was a sticker with a different Serial Number over the laser etched original serial number.

The laptop had a hardware issue with the sound and I looked to see if it was still under warranty for the "New" serial number and it was.

I sent in the laptop and HP service refused to service it because the laser etched serial number on the bottom was out of warranty. I told them that there was another serial number on a sticker that matched the serial number on the box. I was told over the phone by a rep that HP does not change the serial number on refurbished laptop.

At this point I'm feeling I got had but the electronic store that sold me the laptop as it's broken and out of warranty and the serial number on the box isn't for this laptop and they just put a sticker on the laptop to make it seem like the serial numbers matched.

I just wanted some verification.... Does HP ever for any reason change a serial number for a laptop when they refurbish it?

At this point HP is sending the laptop back to me unfixed and I have no way to prove, other than the reciept and the box that don't match the etched serial number on the laptop, they defrauded me...