Windows 8 and 8.1 Forums


Changed UEFI to CSM

  1. #1


    Posts : 1
    Windows 8

    Changed UEFI to CSM


    I have bit off more than I can chew, and I hope someone can help me.

    I bought a Toshiba laptop that came with pre-installed Windows 8. I went into the "Bios" and switched from UEFI to CSM, Now my laptop just doesn't work. I am on a public computer posting this because mine will just not boot at all. It won't even show the boot logo, and I cannot get back into the Bios to switch it back to UEFI. Can anyone help me? I am not sure what information I could add on to here to be more clear other than I screwed up bad. The laptop didn't come with a disk, and I tried to hold 0 while powering up the laptop hoping that it would reset to factory settings, but no luck there either.

    I have exhausted all the searches I can think of. I have dug through these forums, and every thread I found it seemed people were able to get back into their Bios and switch it back to UEFI. I have googled my butt off, and called all my friends that might be able to help. This is really the last shot I have.

      My System SpecsSystem Spec

  2. #2


    Sloe Deth, Californicatia
    Posts : 3,908
    Windows 8 Pro with Media Center/Windows 7


    I'm wondering is "KillCmos" would help, but it may damage your BIOS. Toshiba's have strange F key settings to do various stuff, I'll have to look it up. It was hard enough to get into the BIOS of older systems.

    I found this:

    Toshiba Support Forums: How to access BIOS settings on my ...

    And this:

    BIOS keys for R700 - TOSHIBA FORUMS

    This one says basically the same thing:

    BIOS Access Keys for Computer Systems (Lenovo, Sony, HP, Dell, etc.)

    And then this:

    How do l go to BIOS setup in my Toshiba Laptop,l had tried F10 and F2 but it didn't help? - Yahoo! Answers

    Try each one, one says Press F12 immediately, one says Escape, One says F1. Just try them all until something happens.

    How old is it, I'd take it back and get it replaced.
      My System SpecsSystem Spec

  3. #3


    Posts : 5,592
    ME, XP,Vista,Win7,Win8,Win8.1


    If you would like Windows 8 installed in Legacy mode, you would need to reinstall Windows 8 in Legacy mode,
      My System SpecsSystem Spec

  4. #4


    Sloe Deth, Californicatia
    Posts : 3,908
    Windows 8 Pro with Media Center/Windows 7


    Ah, he needs to change his installation? But from what he's saying his Puter is futzed - Hey Spriggen, will the thing boot with a Bootable Disk in the drive?
      My System SpecsSystem Spec

  5. #5


    Quote Originally Posted by Spriggen7 View Post
    I have bit off more than I can chew, and I hope someone can help me.

    I bought a Toshiba laptop that came with pre-installed Windows 8. I went into the "Bios" and switched from UEFI to CSM, Now my laptop just doesn't work. I am on a public computer posting this because mine will just not boot at all. It won't even show the boot logo, and I cannot get back into the Bios to switch it back to UEFI. Can anyone help me? I am not sure what information I could add on to here to be more clear other than I screwed up bad. The laptop didn't come with a disk, and I tried to hold 0 while powering up the laptop hoping that it would reset to factory settings, but no luck there either.

    I have exhausted all the searches I can think of. I have dug through these forums, and every thread I found it seemed people were able to get back into their Bios and switch it back to UEFI. I have googled my butt off, and called all my friends that might be able to help. This is really the last shot I have.
    Hello. Did you ever get a resolution to this? I had a similar issue last night. I am W7 savy and wasn't a big fan for W8, however, last night I tried to downgrade to W7 to a Toshiba P855-S5312. When changing the boot type UEFI to CSM, now it keeps alerting PXE-M0F or insert a bootable DVD or removable media. I have been trying to access the BIOS under the CSM boot and revert back to UEFI, but neither key seems to access the BIOS. I've tried from ESC up to the DEL keys. If you or anyone on the forum know of a fix, I would greatly appreciate it!
      My System SpecsSystem Spec

  6. #6


    Have you tried unplugging the CMOS battery? That should reset all of the BIOS settings to DEFAULT.
      My System SpecsSystem Spec

  7. #7


    Quote Originally Posted by brucedavis View Post
    Have you tried unplugging the CMOS battery? That should reset all of the BIOS settings to DEFAULT.
    Hey Bruce,

    Thanks for your reply. The CMOS battery is soldered onto two prongs (+,-). Do you know of how to reset these kind of batteries? Again, thanks for your feedback.
      My System SpecsSystem Spec

  8. #8


    Does your battery wires look like these?


    Genuine TOSHIBA Satellite P855-S5312 CMOS Battery, RTC Battery TOSHIBA Satellite P855-S5312 BIOS battery

    The wire attachment should disconnect. Disconnect it for a second and reconnect.

    There is usually a glue that they use to attach the battery. You must be able to replace it at some point. I don't believe the battery is actually soldered to the machine. It should be glue but it is not necessary to remove the battery from it's place, simply remove the connector
      My System SpecsSystem Spec

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