title | description | ms.date | manager | audience | ms.topic | localization_priority | ms.reviewer | ms.custom |
---|---|---|---|---|---|---|---|---|
Can't start computer from a USB flash drive |
You can't start a computer from an external removable USB hard disk that's formatted to use the FAT32 file system. This issue occurs because the USB drive is treated as a floppy disk. Provides a resolution. |
12/26/2023 |
dcscontentpm |
ITPro |
troubleshooting |
medium |
kaushika, huiwu |
sap:Backup, Recovery, Disk, and Storage\Partition and volume management , csstroubleshoot |
This article works around a startup failure when you use a USB flash drive that's formatted to use the FAT32 file system.
Applies to: Windows Server 2012 R2
Original KB number: 954457
You format a USB flash drive to use the FAT32 file system. When you try to start the computer from this USB flash drive, the startup process stops responding, and the screen is black.
This issue occurs because the USB flash drive is listed as removable media. Therefore, the Windows operating system doesn't create a master boot record (MBR) on the USB flash drive when you format the flash drive to use the FAT32 file system. The USB flash drive is treated as a super floppy disk. The FAT32 startup code doesn't support starting a computer from a super floppy disk without an MBR.
The BIOS tries to transfer the control of the startup from the USB flash drive to the FAT32 startup code. However, the FAT32 startup code doesn't support this scenario.
To work around this issue, use the Diskpart
command prompt utility to create and format the boot partition on the USB flash drive.
For more information about how to use Diskpart
, see DiskPart Command-Line Options.
Currently, the Windows operating system uses signatures at offset 3 in the boot sector to determine whether the sector is a boot sector. These signatures don't appear in the MBR. The signatures are as follows:
- FAT16: MSDOS5.0
- FAT32: MSDOS5.0
- NTFS: NTFS
Check two strings in the boot sector to determine if the USB flash drive was formatted by using one of the following file systems:
- FAT32
- FAT16
- NTFS
If the strings contain FAT32, FAT16, or NTFS, the boot sector was formatted in that particular file system format.