Can't boot into BIOS from Ubuntu

A couple of months ago I installed Ubuntu to see the viability of it for day-to-day use. Of course the OS is viable for that, but I wanted to know whether it was for me. So I installed and used it for some time.

Nothing to complain about the OS specifically, but some random issues / reboots and hangs made me switch to good old Windows 10 again. But when I wanted to do that, I could not.

The issue was that I could not enter BIOS by pressing F2 from the boot menu. In fact, there was no boot prompt or TOSHIBA logo (my Laptop is a toshiba C50-A)

After some research in the net I found there's a bug of some kind in Toshiba BIOS preventing the entry of BIOS from boot time.

I tried to insert another laptop HDD, and upgraded it to Win10 using a DVD (from windows) and there was no luck entering BIOS from there as well.

I found the reason for this was enabling "FastBoot" from BIOS. I did that to check whether it speeds up booting. It didn't, but I left it there anyway. I actually forgot all about it afterwards.

There was no way to enter BIOS to disable it. So I finally carried out the following steps:

1. Remove the laptop Battery
2. Remove the CMOS Battery
3. Press and hold power button for 10s
4. Re-insert laptop battery (CMOS is still out of the lap)
5. Power up the lap

Then, BIOS was reset and the fastboot value was set to the default "No".

I was able to boot from the DVD and install Windows 10 afterwards. (I did the above steps which might include senseless steps like keeping the CMOS out for the first boot, but just follow if you're in this situation, might save some time.)

Note: I did not have UEFI enabled at all.

Moral of the story: Do not enable fastboot with Ubuntu if you want to switch OSes later.


P.S. If you want to change UEFI settings, you can reboot to UEFI from Windows 10 Settings > Update and Recovery > Advanced Start-up. Totally unrelated to this, but might give you some idea if you have a separate HDD with win 10 while you have the issue.