By 5:00 AM, the transit authority’s schedule database was back online. The city’s morning buses rolled out on time, never knowing that their entire route database had been hanging by a thread of manually repaired block tables.

Then he ran:

Marcus opened Disk Management (diskmgmt.msc). He clicked Action > Attach VHD . The dialog hung for 45 seconds before spitting out: "Virtual Disk Manager: The virtual disk is corrupted or unreadable."

The sector size was misaligned. The VHD's internal "footer" (the last 512 bytes of the file) was intact—he confirmed that with a hex dump—but the BAT (Block Allocation Table) had a phantom block pointing to a sector that didn't exist.

chkdsk Y: /f /r /x CHKDSK ran for 90 minutes. It reported fixing three orphaned files and two bad clusters in the MFT (Master File Table). But when he unmounted and tried to attach the VHD again in Hyper-V? Same corruption error. CHKDSK fixed the filesystem inside the VHD, but not the container itself.