boot - This computer currently has no detected operating systems (no UEFI)

I am trying to install Ubuntu in a laptop with Windows 8.1, but after launching from a USB, I obtain the message “This computer currently has no detected operating systems”. I’ve seen a lot of similar problems in this forum, but all of them are solved in a similar way, as they are related with the UEFI or Legacy mode. However, my laptop had Windows 7 preinstalled, and I installed Windows 8 later, and when I try to modify these options in BIOS I don’t find anything related with UEFI or secure boot (I’ve already checked a lot of forums but I realized this option doesn’t exist on my BIOS). However I found strange that the USB is detected in BIOS as “UEFI: USB Flash Disk 1100”. Windows 8.1 is installed in Legacy mode, and the partition is MBR.

After a lot of time trying in this way, I created a partition (shrink space in Windows, there are also a lot of tutorials on how to do it in this forum) in order to install linux in that partition. However, when I click “Something else”, all the space is detected as free space. It is, there are no partitions. The only idea I have is to create the partition by using this assistant, but as everything is detected as free space, I will indeed lose everything I have in Windows.

Any idea? Thanks for the help!

Chances are your partition table is damaged, or at least has something quirky about it that the Ubuntu installer doesn't like. The Ubuntu installer relies on libparted, and I wrote a Web page about this problem in parted and related tools here:

http://www.rodsbooks.com/missing-parts/index.html

If I'm right, the easiest way to fix the problem is to run fixparts, which comes with Ubuntu in the gdisk package. It might ask you some questions or simply fix the problem. You may need to type w to save the changes it makes (which it mostly holds in memory until you OK a change).

Note that fixparts can't fix every problem that might cause the symptoms you're seeing. If you're unlucky you'll need to do more extensive repairs. If that's the case, you'll need to post detailed partition information, which you can obtain by typing the following commands:

sudo fdisk -l /dev/sda

sudo gdisk -l /dev/sda

If you've got multiple disks, repeat those commands for all of them.