Why do USB devices cause this?

BIOS may try to read from USB devices during boot. If a USB device sends unexpected data, it can interrupt the boot I/O process.

Can a Windows repair fix this?

If it is a software issue (corrupted boot sector), yes. If it is hardware (bad cable/drive), no. Fix hardware first, then repair software.

Windows Boot Error 0xC00000E9 — Unexpected I/O Error

Criticalboot

Overview

Windows boot error 0xC00000E9 indicates an unexpected I/O communication error with the boot device, typically caused by loose cables, failing drives, or USB boot conflicts.

Key Details

Error 0xC00000E9: 'An unexpected I/O error has occurred' during boot
Windows could not communicate with the boot disk properly
Very commonly caused by a loose or damaged SATA/NVMe connection
External USB devices plugged in during boot can interfere with boot order
Can indicate the beginning of drive failure

Common Causes

Loose SATA cable or poor NVMe M.2 seating in the slot
USB device interfering with boot process (especially USB drives)
Failing hard drive or SSD with intermittent read errors
Damaged SATA port on the motherboard
Corrupted boot sector or MBR on the boot drive

Steps

1Disconnect all external USB devices and try booting again
2Open the case and reseat the SATA cable on both ends (drive and motherboard)
3For NVMe: remove and reseat the M.2 SSD in its slot
4Try a different SATA cable and different SATA port on the motherboard
5Check drive health: boot from USB and run CrystalDiskInfo or manufacturer diagnostics