I need to install Ubuntu as dual boot option on a HP Z800 Workstation which has Windows 7 installed. Ubuntu installer cannot detect Windows and complains "This computer currently has no detected operating systems". I tried to allocated a partition of 200GB of free space using Windows disk manager, and the Ubuntu installer fails to see any free space. The PC features: 24Gb of RAM, dual Xeon CPU, 2TB of disk space. Does anyone know what's going on? Windows Disk Partition image UBUNTU did not find Windows
Do you know, if the hard disk uses a GPT or a MBR structure? If it is GPT, there should be also a corresponding fake MBR. Maybe these two are not consistent.
Some time ago, I had a similar problem. The Ubuntu installer could not detect the fresh Windows 7 installation. I solved it by wiping the first sectors of my hard disk. Then I could create a clean MBR structure and install Windows and Ubuntu again. Before you continue with any experimental steps, you should create a complete backup of your Windows installation.