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I installed Ubuntu version 12.04.3 on my desktop and after that I cannot boot Windows. The computer has two hard disks (one is 2TB, one is 1TB). Before I installed Ubuntu, I have Windows 8.1 installed on the 2TB hard disk. The 1TB hard disk is empty (no partition, no logical drive). I installed Ubuntu in the following steps:

(1) create a Ubuntu 12.04.3 installation DVD

(2) boot from this DVD

(3) Ubuntu installation program shows the following disk partition:

  • /dev/sda (2 TB disk with Windows 8.1 installed)
  • /dev/sdc (1 TB disk, empty, no partition)
  • /dev/sdb (32 G flash drive)

(4) I created two new partitions on /dev/sdc (1 TB disk):

  • /dev/sdc1 (ext4 format with 968 GB)
  • /dev/sdc2 (swap, 32G)

(5) I chose to install boot loader on /dev/sdc (1 TB disk)

(6) Everything was very smooth. But after I restarted the computer, there was no Windows boot option. It directly boots to Ubuntu 12.04.3 user loggin screen. Ubuntu still can access Windows 8.1 disk (/dev/sda, 2TB) and I can access all the files there. But I cannot boot Windows 8.1.

(7) If I unplugged the hard disk with Ubuntu installed (i.e. /dev/sdc with 1TB space), the system still cannot boot Windows 8.1. It stops with the "grub" prompt.

Can anyone help with this problem? Thanks.

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please check if you have disabled secure boot . disabling secure boot may cause this problem. or just press F12 on startup and you will get an option to boot in windows. –  rittik Dec 10 '13 at 4:16
Are both systems installed with either UEFI or both BIOS boot modes? Also better to have / (root) be a smaller 25GB partition and use rest as /home or data partition(s). Post link to bootinfo report. help.ubuntu.com/community/Boot-Info –  oldfred Dec 10 '13 at 4:58

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