Drive 0 Unallocated Space During - Windows Installation

When you reach the "Where do you want to install Windows?" screen during setup, you see a list of drives and partitions. Drive 0 is typically the first physical hard disk detected by your computer's BIOS/UEFI (e.g., the primary SSD or HDD). Unallocated space refers to a portion of that drive that has no partition or file system.