| Visible in BIOS, missing in File Explorer | Drive is uninitialized, formatted with an incompatible filesystem, or lacks a drive letter | diskmgmt.msc | Initialize disk as GPT, create a Simple Volume, and assign a valid mount letter. |
| Drive not detected during Windows setup | Intel Volume Management Device (VMD) or RAID controller hides raw PCIe endpoints | BIOS / Setup USB root | Disable Intel VMD in BIOS or load the Intel RST VMD driver via the setup screen. |
| Drive absent in both Windows and UEFI/BIOS | M.2 slot shares PCIe lanes with disabled SATA ports, or M.2 standoff misaligns pins | Motherboard PCB / BIOS | Move drive to the primary CPU-attached M.2 slot and verify lane bifurcation settings. |
| Disk Management shows “Unallocated” and errors out | Windows Storage Spaces pool has claimed the drive or metadata lock prevents write | control /name Microsoft.StorageSpaces | Delete the disk from the active Storage Pool and clear all pool metadata via diskpart. |
