I was trying to setup a USB stick contents a standalone ubuntu OS which would let my win8 ultrabook more "producable".
In the end, I messed up my bootloader to have a ubuntu boot option which should be on the usb drive, and I do not even get my USB drive ready.
After several try on googling the answer on how to remove that ugly boot entry, I finally figure it out.
The way is much more than simple,
no need to delete it by efibootmgr(ubuntu), bcdedit(windows), or download the easyBCD software.
All things you gonna to do is
(1) boot your device into a ubuntu live CD which should you prepared for ubuntu installation.
(2) check which partition does EFI entry located by "gparted" (it should format in FAT32)
(3) mount it on, for example,
mount -t vfat /the-efi-partition /whatever-mount-point
(4) cd in the directory and you could find the ubuntu boot entry: EFI/ubuntu.
(5) remove the entire folder: rm -rf EFI/ubuntu
That's it, you get it.