I purchased a few days ago an Acer Aspire E15 not knowing BIOS have been replaced by UEFI, trying to installl Debian 7 alongside Windows 8.1 is a real hassle. After many unsuccessful attempts I managed to install it after doing this:
-disable Windows 8.1 "fast starting"
-disable Windows 8.1 "secure boot"
-allowing first boot option to be DVD drive
-shrink Windows 8.1 partition to 50GB but this had to be done with the Debian partitioner because an error made under the Windows procedure could not be corrected under Windows
-partitionning accepted the ESP partition as-is and installing started automatically
-some attempts at selecting mount point for the ESP Windows partition as /boot/uefi as recommended in some tutorials/howtos had not work giving message: "uefi partition not found"

the Installer seemed to have failed installing GRUB so, after it asked to remove the first installation DVD in order to reboot, it rebooted into Windows 8.1.

My questions are:
Do I have a salvageable Debian 7 installed and bootable? How?

Or, how can I safely wipe out this rotten Windows OS and install Debian 7, I fear I may still have problems with UEFI.

I have found a lot of info on the Internet but none pertaining to this particular situation.

Thank you for your help.

Is there a option like "legacy bios" or "compatibilty boot mode" in your bios?

rblampain,

As you know, use F2 to enter Setup.

You have already disabled Secure Boot and Fast Startup.

You may or may not need to set a Supervisor password temporarily (see Security tab) in order to allow you to change more settings.

Disable UEFI and enable Legacy mode.

Before doing the next part, make sure that your Debian 64 bit DVD or USB drive is inserted.

In Boot > Boot Order, put DVD or USB HDD at the top of the list, by means of F6, and press F10 to save and exit.

When the laptop starts again you may be asked to press a key to select the Boot Device.

In addition you may be asked to type a 4 digit code to confirm your boot device selection (and your disabling of UEFI).

Debian or other Linux should now load.

Remember to remove the Supervisor password later if necessary.

I think you should probably try Debian 8 as it has better EFI support (Debian 7 does not support 32-bit systems or 64-bit systems with 32-bit UEFI firmware).
http://cdimage.debian.org/cdimage/un...ding-firmware/

Mark the extant EFI system partition explicitly as the "EFI system partition" in the installer and it should work fine -- I have done this myself today with a Debian 8 netinstall ISO image (typing this from that system).

You could try to rescue the system you have already installed by following this guide:
https://wiki.debian.org/GrubEFIReinstall

Agreed with Head_on_a_Stick. Debian 8 works great with UEFI, and as long as you don't have secure boot enabled, then it'll be easy to set up. In fact, it's even easier if you DON'T have legacy mode enabled, as it will automatically boot UEFI and mark the EFI partition as such.

Even Debian 7 should be installable on an UEFI machine, even without the legacy boot option.

The thing you definitely need to turn off is secure boot. As far as EFI support in Debian 7 is concerned, you just may need an extra few steps to get it running as the installer won't pick it up by default, but it still can be done.

Back in 2012 I did just that on an UEFI Laptop. I actually installed Crunchbang Waldorf, but that is a Debian 7 based distro, so the approach should work the same. After I had it working I posted my steps to success in the Crunchbang forum, and the post is still online. You can find it here.

Note that you might even get away without the part of manually creating boot entries in your efi menu through the efi shell (step 4 in the step-by-step guide).

Debian 7 is now an old release you might as well just install Jessie it's the stable release now. Also you may have to make room for the debian EFI partition.

rblampain,

You may wish to consider using an alternative to Debian such as Linux Mint MATE 17.1 (64 bit):

http://www.linuxmint.com/edition.php?id=174