Hi! I have an NP300E5C, ita version. And yeah, same issue. After some long researches, it came out that installing linux on these laptops, corrupts the NVRAM. For this reason, the bios becomes not accessible anymore, and the os doesn't boot anymore. Other drives won't boot too. Try to enter the boot menu pressing some random F keys. If this doesn't work, unfortunately you can fix only by replacing the bios chip (costs around 15€ on ebay, not really expensive)