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I'm trying to downgrade a Toshiba Satellite C55T-A5123 that came with Windows 8.1 on it to Windows 7 x64 bit. I'm stuck at not being able to get it to boot the installation media. I've turned off secure boot and tried both from a DVD and from a USB flash drive.

I've verified another PC will successfully boot both the DVD and USB flash drive, so I know they are not the problem. When I turn on the laptop, I'm hitting F12 to get the boot selection menu and after I select the DVD or USB flash drive option, it just goes on and boots from the hard drive into Windows 8.1. I've even tried changing the boot order in the BIOS/UEFI setup. I also read one suggestion about going into the BIOS/UEFI setup and changing the boot mode from UEFI to CSM, but that option is nowhere to be found.

Also worth mentioning I am making sure that Windows 8.1 is completely shutting down by using the Shift key method. I've even resorted to pulling the plug and battery to make sure.

Also worth mentioning I've verified the DVD drive and USB thumb drive are visible once the laptop boots into Windows 8.1. So, I know that's not the problem either.

I've installed every version of Windows from MS-DOS to Windows 7 and dozens of GNU/Linux distributions so many times in my life I cannot even count them. I've even installed Gentoo for crying out loud and I've never had this much trouble getting the install media to boot.

Any suggestions?

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  • You are 100% sure you are changing the boot order, you choose to restart the computer at this point after you save the settings, correct? Are the settings being saved?
    – Ramhound
    Commented Apr 6, 2014 at 0:46
  • @Ramhound, yes.. 100%. I've gone back and double checked. As mentioned, I've even tried from the one-time boot selection menu.
    – Drew Chapin
    Commented Apr 6, 2014 at 0:49
  • Other settings are being saved correct?
    – Ramhound
    Commented Apr 6, 2014 at 2:41
  • Have you tried changing the hard drive? It may be a hardware issue.
    – superuser
    Commented Apr 6, 2014 at 2:55

2 Answers 2

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Do you have legacy boot enabled? If not first try to enable it and try booting from your CD/USB again.

If that doesn't work, this might be a problem with the BIOS it self. What is your current BIOS version? Is it below 1.30? If it is, I suggest the first thing you try is to upgrade your BIOS by downloading the latest version here. I doubt you have the latest version since the website claims it was posted 3 days ago (4/2/2014) The website I linked contains both instructions on how to flash the BIOS and the download. I read through the instructions and seems like your BIOS should have CSM Mode from this statement in the website.

Go to the Advanced tab, enter "System Configuration" and set the Boot Mode to "CSM Boot."

But then again it might not because in the change history for the latest version it states:

Added: CSM mode support.

Try that and let me know how it goes.

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  • As I mentioned, there are no options for CSM or "boot mode". In fact, other than boot order and secure boot enabled/disabled, there are no other boot related options. I generally don't like upgrading the BIOS unless I absolutely have to, but it's worth a shot I suppose. I'll let you know how it turns out.
    – Drew Chapin
    Commented Apr 6, 2014 at 1:47
  • I am not sure the point of doing this to be honest. CSM isn't the answer thats basically legacy mode, which means, no GTP partitions.
    – Ramhound
    Commented Apr 6, 2014 at 2:41
  • After upgrading the BIOS, the CSM option was available and I could boot from the installation DVD.
    – Drew Chapin
    Commented Apr 6, 2014 at 17:13
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The CSM mode switch is found in Toshiba Bios by pressing FN+F2 at the Toshiba post screen. You will need to use the touch screen to navigate. While the mouse will work in performing any changes may not save correctly without using the touchscreen.

The option is located under the advanced tab. Now I do need to make the point that Toshiba, like other manufacturers of this style of Windows 8.1 PC, did state that they did work closely with Microsoft on measures which prevent Windows 8.1 from being removed as the dominant operating system.

I would recommend enabling the visualization and installing Windows 7 as a secondary. Over 90% of the hardware does not support Windows 7 so you may loose functionality. If the Windows 8.1 metro interface is the issue I would recommend looking at tech net on how to disable metro in Windows 8.1

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