legacy bios mode crashes Windows 8.1

i doubt you would even care at this point about your problem, but if you still want to know,

The Unified Extensible Firmware Interface UEFis a specification that defines a software interface between an operating system and platform firmware. UEFI replaces the Basic Input/Output System (BIOS) firmware interface originally present in all IBM PC-compatible personal computers, with most UEFI firmware implementations providing legacy support for BIOS services. UEFI can support remote diagnostics and repair of computers, even with no operating system installed.

UEFI (or EFI) comes preinstalled on windows Operating systems Windows 7 and up.   anything before that used BIOS (basic Input Output System)   they essentially are the same thing but UEFI handles the boot process differently.  Unlike BIOS, UEFI can allow you to boot into recovery options, such as the command prompt, BIOS (Not the boot type. however BIOS is pretty much a generic term for the boot options and everything) settings, UEFI can also support disks over 2 TB in size (With GPT [GUID Partition Table]). (Oh and UEFI is a lot prettier)

as far as i know, UEFI checks the boot loaders keys and signitures to verify that it is a non malicious program.  This is where secure boot comes in.  Secure boot is basically the "anti virus" of the boot manager.  It verifies that he boot loader is safe and what not.  

The Downside to this is that UEFI ONLY supports booting with UEFI Windows OS's, which are windows 7 and up, and blocks other UEFI or EFI systems from using the windows boot loader.

However, BIOS doesnt do that.   Your computer is not broken so dont worry about reinstalling it or anything.  your situation was normal.   The reason you cant boot your windows OS in legacy/CSM/BIOS mode is because BIOS mode cant boot the modern windows boot loader, and UEFI cant boot the old windows boot loader.   The reason you had to switch boot modes to get into linux was because your particular linux distribution was setup to boot in bios mode.  

However there is a way around the dual booting block that microsoft did with UEFI.  and that is to make sure that your linux is booted into UEFI mode (before installing it, also research how to do this because it would make this way longer than it should be), and then when you install linux, make sure that you mount the boot loader to /boot/efi, or choose the main partition (/dev/sda) (research like i said to make sure)  because once this has been done, the GRUB (Grand Unified Bootloader) will overwrite the Windows Bootloader as the one that would boot windows.   So instead of the Windows Bootloader running your computer, the Linux GRUB loader would be  However there is ANOTHER problem with this...

If GRUB is your main boot loader for windows AND linux, it can render your computer inoperable for a limited amount of time (by that i mean until you rebuild the boot loader and what not, ill provide a link for this)   

If something happens to the Linux OS, for example, you wipe all the linux partitions, includeing the boot, swap, and main partition, and you leave only your windows ones, GRUB cant find anything to boot to (windows boot manager was chainloaded to GRUB) so when you turn your computer on, you be stuck in grub recovery mode, because you wiped the boot loader partition FOR grub.   The Windows OS is still untouched, however theres no way to access it.

I know this is a mouthful but i hope it answered some of your questions.  haha and if this doesnt make a lot of sense, just research it.  

Heres how you can rebuild your Windows Bootloader just incase you cant access it because of GRUB being wiped, or for any other reason it wouldnt work:

http://www.fixedbyvonnie.com/2013/12/how-to-repair-the-efi-bootloader-in-windows-8/#.V09tfiuqOM8

This only rebuilds it, it doesnt touch any other part of Windows. your files will be safe.

IF you need further explaination, i can help haha

Your license key is usually in the battery compartment of a laptop, or on a sticker on the bottom of the machine. If you are using a desktop, the sticker is on the outside of the PC or inside the removable side.

The factory has to provide the license key to you. If you did not erase Windows 8.1, why don't you just boot up to the recovery partition and restore it that way or if it will go into 8.1, go out to Settings and then refresh the system. That way it won't get rid of your files.

Thanks for detailed response. Both links require product key. Even though windows came with the purchase of my laptop Acer v3, I do not have the product key but s/n and snid on the back panel, and it is not printed on the receipt from the store, Fry's either.

Secondly, I can access Advanced Start Up through PC settings but repair fails. And let me make it clear that my windows is working just fine with EUFI bios mode. Its only when I change the mode to Legacy Bios mode, it crashes trying to boot Linux on a partition L:\ which I previously had but deleted now.

Did Legacy Bios work before I installed Trisquel Linux? I do not know because only after I installed Trisquel and rebooted, when Windows loaded without giving me dual boot option, I went to bios mode and changed to Legacy Bios, which loaded Linux only and not windows. But of course after changing to EUFI mode, windows would load just fine.

I am not even sure at this point if this is normal for Legacy Bios not to load windows 8(now 8.1 updated) or is it? Has installation of Trisquel actually left Grubs in to my windows MBR or not? I did not get dual boot option at all before and after the install and uninstall of Linux.

Is windows 8.1 supposed to load with Legacy Bios option as well?

Since I don't have product key, what would be my next alternative without having to Refresh or Reinstall windows from recovery? I have heard even with format of C:\ grubs is hard to get rid of, is that true? If so, this seems like a deliberate attempt of Linux distributor to attack on Windows users, no?

Thanks

Hi Masikwha,

You will need the Windows 8 installation disc to perform an Automatic repair. If you don’t have a Windows 8 disc, I would suggest you to download the Windows 8 installation files from another computer through this link and choose to “create an installation media” when the upgrade assistant prompts.

http://windows.microsoft.com/en-US/windows-8/upgrade-product-key-only

http://windows.microsoft.com/en-US/windows-8/create-reset-refresh-media

Once you have a Windows 8 installation disc, follow these steps:

1. When your computer starts, wait for the manufacturer logo to check the option for boot menu, it will usually be F12.
2. The boot menu key might differ with each manufacturer. If you are unable to find the boot menu key, you may refer the user manual.
3. Restart the computer, when the manufacturer's logo is displayed, keep pressing the Boot menu option key to enter the boot menu and change the boot option to CD\DVD ROM.
4. After you boot your computer using Windows DVD or System Repair Disc, a black screen appears with gray text "Press any key to boot from CD or DVD". Press any key.
5. Select the “correct time and Keyboard type”.
6. Click “Repair your computer” in the lower left corner
7. Click on “Troubleshooting”, “advanced” option and then click “startup repair”.

Reply with the status of the issue and we will be glad to offer our assistance.