My computer specifications:
64 bits computer.
Intel(R) Core™ i5-4460 CPU @ 3.20GHz 3.20 GHz.
4 gb ram.
MBR partition table.
Bios (not UEFI system).
I have installed windows 10 again and then I have installed Lubuntu 20.04 with manual partitioning.
I have got the grub menu, but when I choose Windows10 sometimes boots w10 and sometimes doesn´t boot so I don´t know what to do.
When I select Windows10 in the grub menu and doesn´t boot I get a black screen where everything I do with the keyboard is useless so I have to power off the computer.
This is my disk with Windows10 before installing Lubuntu 20.04.
Then in the unassigned space (780,95 GB) I have created a logic partition with four partitions inside:
/boot: 1gb ext2
/: 30 gb ext4
/home: 745,9 gb ext4
Any idea, why do I get sometimes a black screen when I boot with Windows10?
When I boot with Lubuntu 20.04, It always works perfect.
Could it be that in the grub menu the “/dev/sda1” line for Windows10 should be “dev/sda2”?
(*) Edited 1:
I have discovered two things:
i) when I boot first with Lubuntu and then do a reboot and boot with Windows10, It works.
ii) when I boot first with Windows10, I get a black screen but the system is loading the login screen because if I do this sequence (with the black screen): intro / put my password / alt + f4 / intro / the system switch off, wich is the same sequence I do with windows 10 working properly (without black screen) so I think it could be a problem with the graphics card.
(*) Edited 2
I have found the answer for the problem. It is something that I did one year ago but I had forgotten it.
In Windows 10 I had to disable the fast startup because it affects to grub, so I did that and there is no black screen and W10 boots fine. (Control panel / Power options / what the power buttons do / Change settings that are currently unavailable / turn off fast startup.)