I want to set up RAID 1 across four drives for the OS and RAID 5 across the same four drives with all my extra space. I have four 160GB identical drives. My only problem is that the OS is already installed. Do I have to necessarily have to reinstall the OS or is there another soultion. Please enlighten me on this subject. Even if I have to reinstall the OS how can I make it so I can get the setup that I want? Keep in mind that I can only have a maximum of three of the four drives connected at once during installation because of the fact that I need an extra IDE channel for my DVD drive. No I don't have any extra USB drives or any other option because I am using a relatively old NAS device.