Changing the BIOS setting from UEFI to CSM and disabling the secure boot prevent the notebook from booting the Win 8!
Therefore the unit cannot find the bootable device and switches to last option: LAN.
But since the notebook cannot find bootable system via LAN, the error “PXE-E61: Media test faliure, check cable” appears.
If you want to use a dual boot, you have to boot into Win 8
In Win 8 you have to create an partition for Linux installation. This can be down in Win 8 disk management. You have to shrink an last partition and have to create new one on the available free space.
Now to start the Linux installation you need an media.. you can burn the Linux iso on DVD or an bootable USB stick. There are many details in internet how to create such media.
Once you have created the bootable USB, restart your PC with connected USB.
Press F12 to get the boot menu. Now you should see the USB memory stick (if bootable!!!) choose USB and you should be able to install Linux (Ubuntu is great!)
Now some more weir things.
I use a bootable ubuntu Ubunbtu CD and install the distro (resizing with partition magic).
Now when starts up It goes directly to Ubuntu. But is not posible to shutdown. Only restarts...
If F2 does not work for You to enter the BIOS, You can instead try F12.
As with F2, F12 is a thing of TIMING!
So either learn when to press it (when the Toshiba-logo is displayed) OR hold it down right from the start.
This should bring you to the BOOT menu. From there You should be able to choose
Concerning the reboot, this is probably a kernel bug. I have seen the exact same problem on a unit I have access to.
You can avoid this by pulling out the power-plug just before turning on. That will make the unit shut off properly.
I'm dealing with my own headaches trying to install ubuntu on a P875 with a 750GB drive, but I have learned a few things which might be helpful here.
1. I turned off secure boot simply to get my burned ubuntu installer disks to boot. That setting does not keep me from booting to Windows 8. Changing from UEFI is probably a different story.
2. This applies to my laptop, maybe it applies to yours:
If you need to bring up a BIOS menu when you boot, make sure the boot speed is normal, If the boot speed is set to fast, F2, F12 and other keys won't be checked.
3. I ran into a situation where the laptop was booting straight into ubuntu, but I had normal boot on so I was able to hold down 0 while powering up to bring up the recovery options. You may need to use a recovery disk.