Ubuntu – Boot-repair Boot Info: dual boot Windows 8 and Ubuntu

Here is a step by step on how I did it:
1. Install Windows 8.1
2. disable secureboot in bios (or in some cases allow it to run other Os's)
3. turn off fast boot
4. install ubuntu alongside windows.

Many Sonys have cruddy firmware (EFIs) that refuse to launch anything but the Windows boot manager -- that is, EFI/Microsoft/Boot/bootmgfw.efi. The only workaround I know of is to replace that file with GRUB (or, if Secure Boot is active, with Shim, with GRUB stored in its normal filename in the EFI/Microsoft/Boot directory). The Boot Repair program can do this automatically, but you must enter the Advanced menu and select the appropriate option, which is called something like "back up and replace boot files" (I don't recall the precise wording).

Another thing you might try is replacing the stock Windows installation with a fresh install from retail (not OEM) disks. See here for information on how to obtain various Windows installation media legally. The point of this procedure is to remove the manufacturer-specific cruft that infests most computers and that can add an extra layer of complexity to the boot process.

The most radical solution is to re-install everything in BIOS/CSM/legacy mode, bypassing EFI-mode booting. The limitations in the Sony apply to EFI mode only, so a BIOS-mode boot should bypass these problems; however, such a conversion would be tricky to carry out without a full re-install, and even with a re-install, there will be problems. See my page on CSM issues for details.

I know you say you've tried much of this and it hasn't worked. Unfortunately, your problem is that you've got a defective computer. If you hadn't had it for so long, I'd suggest you return it to the store for a refund, but I doubt if they'd take it back after two years.