I bought a new computer which came with Windows 8 preinstalled. Then I installed Ubuntu 12.04 on the same hard drive, after making a partition with GParted using the "Try Ubuntu" option in the Ubuntu installer. Everything worked fine, I had Windows 8 and Ubuntu working together without any issue.
The problem comes when I decided to install Windows XP alongside with Windows 8 and Ubuntu. It seems that Windows XP deleted the GRUB bootloader, so now I can't boot any OS, there's no Ubuntu option, no Windows 8 option, nothing. Just the message "Read error" (translated from Spanish). I successfully reinstalled GRUB, using the Ubuntu live CD and running some commands from the terminal following a recovery guide, so now I'm writing this from my Ubuntu system, but there's no way to run Windows 8. Now when I select the "Windows 8 Loader" option it says
Read error. Press Ctrl+Alt+Delete to reboot.
So how can I recover the access to Windows 8?