I have researched this and tried the suggested solutions and haven't been able to fix it in my case.
I have a Dell Inspriron 15 R SE.
It came pre-loaded with Windows 8. I booted into the BIOS and turned off EFI security and installed Windows 7 and I'm now trying to install Ubuntu in a dual boot situation.
When I run the installer it tells me there is no OS installed but, when I read up on this it says that you can run
sudo os-prober or
sudo WINOSDATA=true os-prober.
It finds my Windows 7 installation. However when I run
WINOSDATA=true ubiquity, I still get the message saying there is no OS installed.
I have split my 1TB drive putting aside a ext4 partition (about 350 gb) and a linux-swap partition (5 gb) for the installation, but it's only picking up the whole 1TB drive and not the two partitions I created and of course it doesn't see the windows installation.
edit: I have also ran gparted when booted into the live cd. It only sees my HD as one big 1TB partition. It does not see the swap partition or the ext4 partition I created nor does it mention anything about windows being installed
What else can I do to get Ubuntu installed? Thanks in advance!