Happy new year to you and thank you for answering so quickly.
The problem was i hadn't find the way to authorise the mbr or the uefi
writing in the bios.
Now, all works fine (Xubuntu and win8.1), but there is a message saying the
laptop is unprotected just before the GRUB prompt.
However, this
Your EFI system partition is corrupt. You will need to fsck it from
linux or chkdsk/scandisk it from Windows to repair it.
** Changed in: grub-installer (Ubuntu)
Status: New = Invalid
--
You received this bug notification because you are a member of Ubuntu
Bugs, which is subscribed to
