operating system not found
 

Laptop is TOSHIBA Satellite C55-A PSCF6U-01Y00C

Am on Windows 8.1


Any time I restart and my usbs are pluggd in, after the Toshiba logo comes on, I get - operating system not found, try disconnecting any drives that don’t contain an operating system. Press any key to restart- and when I press Enter it goes to the desktop. If my usbs are not plugged in ,I do not get the message.


Strange that the computer repair where I took it for another problem about two months ago and this problem started said they did not know how to fix it. I am 80 years old and need detailed instructions. Thank you. Anna Ruth

Hi foxygrandma, welcome to the forum :).

The solution to your problem is very simple. Simply remove the USB drives when you boot the computer, and the computer will boot up fine.

This happens because the computer tries to search for an operating system on the USB drives, and it does not find them. So, just remove the drive.

Is it required for the USB drives to be plugged in when you start the computer? If yes, why?

If no, then you just remove the USB drive.

Your problem is likely to be because a technician has changed the boot mode from UEFI to CSM (Compatibility Support Module) which allows booting from legacy (old-style) MBR (Master Boot Record) drives because it looks at the boot sector on a drive and ignores the partition table that UEFI uses. This is done so someone can boot from a different drive with their operating system and run their own diagnostics and software on your computer without changing the software and settings that are already stored on your computer's drive.

If you change the boot mode back to UEFI then your computer will not try to boot from USB because that feature is not supported unless you are in CSM mode.

This Toshiba support webpage shows what was done and you just have to reverse it by resetting it back to normal:
1. Power on the system and while the "TOSHIBA" logo appears, press [F2] key to enter the BIOS Setup Menu.
2. Select [Security] tab and set the “Secure Boot” to “Enabled”.
3. Select [Advanced] tab and go to “System Configuration”. (Refer to <Pic.2>)
4. Set the “Boot Mode” to “UEFI Boot”. (Refer to <Pic.3>)
5. Press [F10] key to save and exit.

Hope this is detailed enough for you ... and that it works for you. :) I don't have a Toshiba laptop to test in on.

Good info Remah. Besides the boot mode, how about changing the boot sequence if available?

Yes, that is another option.

I was initially going to mention that but I can think of two reasons why that would only be a partial fix:

• It seemed unlikely that the shop only changed the boot sequence as somebody would also have to disable the UEFI boot settings which are enabled by default on these laptops. It doesn't sound like foxygrandma consented to this.
• UEFI Boot and Secure Boot makes Windows considerably more secure. It isn't something that foxygrandma should have turned off.

@Remah, strangely enough, on my Lenovo laptop, toggling the "Boot" setting from UEFI to Legacy (or vice versa) automatically changes the Secure Boot setting too. I don't have to touch the Secure Boot setting at all.

Its not the strange because they go together. It's two steps to disable because Secure Boot won't allow CSM/legacy mode. It probably doesn't have to be re-enabled in two steps on the Toshiba but I included them both just in case.

Remah, I'm not doubting that it's a 2-stage process on the OP's computer. For that matter, every article I've ever read says you must disable Secure Boot and change the Boot Mode to Legacy/UEFI. All I'm saying is that on my laptop I only have to do one thing, i.e. change the Boot Mode to Legacy/EUFI. In other words, I don't ever have worry about toggling Secure Boot, and that is what I find strange. Also, just to make to be sure I'm not imagining things, I tried it again and confirmed it is so.

Joe A.TT, I was saying that it makes sense to do it in one step as Lenovo has. The only reasons that I can think of for turning off Secure Boot are troubleshooting issues in which, for example, the legacy mode is needed to boot from other devices.