I used to have Ubuntu on my Dell laptop. 2 days before, it suddenly shut down after watching some Youtube videos. Then it simply and always shuts down during booting, some time after logo screen. I decided to install new and most up-to-date version, both install and LIVE shut down laptop. Then I tried Linux Mint, lubuntu, Linux Lite, Peppermint, Arch, Puppy, ... All of them failed, install or LIVE.
I know it's not hardware, cuz Windows on this same laptop still works.
I recently upgraded from 4GB RAM to 8GB RAM. I've also removed the new memory stick, and the situation is the same.
What is the most likely cause of this issue?