I just purchased a Toshiba Qosimo X75-A7298 laptop and want to install Ubuntu on it (don't particularly care which version). I tried both V12.04LTS and 13.10. The boot process hangs almost immediately after I choose to "Try Ubuntu without installing". I turned off "secure boot" and changed the boot mode from "UEFI" to "CSM" with no luck.
Try fixing the video problem before switching modes. For UEFI machines (with a black screen grub (grub-efi) without any function key options, like the older grub-pc, edit the grub menu and add the below options on the "linux" line, then boot with F10 or ctrl-X.
Options for Video problems:
To allow Nvidia hybrid machines to boot.
I've successfully installed Ubuntu 14.04 on the Toshiba Qosmio X75-A7298. Here's where I got the iso:
Basically, I just burn the ISO called "trusty-desktop-amd64.iso" to a DVD.
I pressed F2 a few times, right after turning on the Toshiba Qosmio X75-A7298. That took me to the bios and I too disabled secure boot and changed the boot mode from "UEFI" to "CSM" in the "Advanced" section of the bios.
After saving these changes and rebooting, this time I held down the "c" key so that it would know to boot from the dvd I burned.
The only issue I'm now having is I can't figure out how to adjust the screen brightness: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1295141
Oh, and by the way. This laptop runs Ubuntu 14.04 blazingly fast.