So I've been trying to install Ubuntu on a second HDD on my desktop, which has W8 installed on a SSD (UEFI-only boot). Thing is, during Ubuntu installation I made the mistake of choosing to install the bootloader (GRUB) to the first disk (the SSD), and after install I could not boot into W8 (the entries in GRUB didn't work). Following these instructions, I managed to be able to get "Windows Boot Manager" back, however I lost GRUB in the process, and got a duplicate "Windows Boot Manager" entry in BIOS, along with the "Ubuntu" entry, which then I used to boot into Ubuntu.

Later, I decided to reinstall Ubuntu, and formatted the HDD from within windows, however, the entries in BIOS stayed the same, and, while I had the HDD connected to the motherboard, I could not boot into an Ubuntu Live USB (in order to reinstall Ubuntu).

I made another mistake by updating the BIOS, which cleared all of the EFI boot entries in BIOS, and, right now, I get an error when boot from the SSD:

grub: device not found (...)

So it seems that grub is still installed in the EFI partition of the SSD, and since I don't have the WBM entry in BIOS anymore, I cannot even boot into Windows, and the previous instructions don't work anymore. Is there another way to reset W8 EFI partition to the default?