Like I said turn of secure boot or die.
It is easy to confuse how to mess up getting windows 8 off a device. You DO need to do things that the average joe would not do. That is dump the need to check the bios signing keys. It is rather hidden and not something that seems to be a good idea. However by turning off the security key check you DO NOT repeat DO NOT stop UEFI bios features accessing HDD partitions larger than 2 gig if you are running a 64 bit environment. The bios will still boot a loader from the MBR (master boot record) that Windows 7 or Linux or whatever writes to the HDD.
This makes the average joe think that by turning bios singing keys in the bios then their install will be somehow insecure and thus they will be instantly "hacked" by evil Russian or Chinese communist hackers.
You be the judge, if this were the case then every single current window 7, vista, and XP install on planet needs to be eliminated immediately for the sake of US national security and the very future of Microsoft LOL