You can install this to an empty, blank disk or to a GPT disk that already has an OS. Unlike BootIt Bare Metal, unallocated free space is not required for a BIU install. BIU installs into the EFI System Partition. Installing an OS sets up the Boot Item so you are ready to go. When you have multiple Windows OS you should confirm the booted OS will see itself as C: drive and all other Windows OS will be hidden so there can't be cross-talk. This information is in Boot Edit. To add an extra OS, create a partition in Partition Work (NTFS or Linux), boot the install media and install to the partition you just created. Disk Imaging: Image for UEFI (IFU) creates and restores the same images as IFW and IFL. You can run IFU manually or from scripts. It is currently CUI but should be GUI shortly. BootNow is supported so you can choose the next OS to boot from your current OS. It isn't necessary to choose the item from the BIU Boot Menu. Theoretically your mufti-boot could contain over a thousand OS. As a minimum I like a Windows OS, a Linux OS and a clone of one of these OS for "experiments". To clone an OS to somewhere else requires 5 mouse clicks. The OS partitions can be on any disk and you don't have to disconnect disks to install subsequent OS.