Hi all, I've got an Imac from my wife's former company that hasnt been cleaned before we got it. It is a late 2012 model with Yosemite as a running system. Originally Mountain Lion was installed. I wanted to clean everything and set up the original Mountain Lion via Internet Recovery. First, i was not possible to install Mointain Lion due to the error You can't upgrade because a newer version is installed! Next I tried to delete the Macintosh HD and the Recovery HD, wich was also not possible. After installing Mountain Lion on an external harddrive and boot from there, it was possible to erase the Recovery HD, but after that I couldnt boot the Imac, only the Internet Recovery (cmd + alt + R) or from the external harddrive. Now I found out the problem is the Fusion Drive on my Mac. Again, with some help in a german forum I could start the Terminal. The command diskutil list brought up the following: The command diskutil cs list brought up this one: As far as I know I need to delete something in order to devide the SSD and the HDD. I am not familiar with the terminal, so I really hope someone can help me. I think this needs an expert, since in the German forum noone could help Thanks in advance!!!