I installed windows 8.1 on my new laptop PC in legacy mode and allocated a separate partition for my other favorite operating system Ubuntu. But when I try to install Ubuntu 14.04, the partition table is not shown correctly and shows the whole space of the disk as free space. I opened Gparted partition editor in Ubuntu and checked as well but the result is same. Moreover, in the Gparted, a message is shown complaining about GPT partition table. As per my knowledge, after searching through few forums, I found that the GPT(GUID partion table) is corrupted or something and we need to remove that. Then I used the following command thanks to this forum. You need to replace sda with your device name which appeared in the installation table.
sudo sgdisk --zap /dev/sda
Surprisingly, now the partition table is shown correctly on my Ubuntu installation. Then I installed the Ubuntu 14.04 in the usual way. After the installation I restarted the PC and the boot-up is appeared with the usual Ubuntu grub having Ubuntu 14.04 installation alongside with windows 8 loader.
If you use UEFI system instead of legacy mode, The procedures may be little bit different but I have no experience about that.
Kavinga's tech thoughts 