How to fix green-pink pixels appearing randomly and sound distortions?

I bought an older laptop (Lenovo ThinkPad L530) for an older relative to use for office and browsing the internet. Unfortunately, the laptop displays clusters of green-pink pixels that flicker and appear randomly on everything. They appear before laptop enters windows, so I thought reinstalling drivers or windows would be pointless. I also tried closing and opening the lid, moving the laptop, and shaking the power adapter cable (it only works plugged, battery is dead) - no change. The problem appears when the laptop sits unused, shut down and disconnected from the socket for a while. After I o

Question by Alex Ch on Super User, licensed CC BY-SA. We show a short excerpt and link to the original thread as credit.