I have a notebook HP 650 and I removed Windows 8 to install Windows 7. I have disabled Secureboot and installed Win7 successfully.
When I boot Ubuntu live cd, the installation manager is unable to detect Windows partition and it is showing all the HDD as "unallocated" so I have no way to resize partition and install Ubuntu without destroying Windows partition.
Same thing is happening with Gparted that prompts me that cant detect if HDD is GPT or not.
Searching internet I found that HP notebooks have a RAID controller that prevents Windows to be properly detected but using the command sudo dmraid -rE I get the "No RAID detected"
I have been setting dual boot frequently for friends etc but this is the first time I can't find a solution.
The most strange is that this notebook is Ubuntu certified http://www.ubuntu.com/certification/hardware/201209-11786/