When a flash drive works on one system but doesn't on another computer or device, it is an indication that the device unable to read the drive may have a compatibility or settings conflict. The good news is that if one computer or device is able to read the flash drive, the drive is not broken and doesn't have corrupted data. However, you'll need to identify the problem with the system that cannot read the flash drive.
Using Compatible File Systems
Storage devices like flash drives use filesystems to format and arrange saved data. A computer or similar device must be compatible with the file system in order to make sense of the stored data. Some file systems, like NTFS and HFS+, are proprietary formats for Windows and Mac OS devices. A Windows computer can't recognize a HFS+ formatted flash drive, while a Mac can't recognize a NTFS+ formatted flash drive. However, flash drives that are going to be used for cross-platform data transfers can be formatted in the ExFAT or FAT32 file systems. Changing a flash drive's file system format will erase all data on the device.
Disabling Plug and Play Devices
The computer recognizes devices added to the system after the initial power-on and automatically configures them with a feature called plug and play. Disabling plug and play on the computer can prevent the system from recognizing external storage devices like flash drives when connected to the computer. Plug and play can be toggled in the CMOS and Device Manager. Plug and play is enabled by default feature, which means it would have to be manually disabled on a system to cause device detection problems. Rebooting the computer can help clear plug and play errors.
Working Around USB Hub Conflicts
USB hubs can connect to up to 127 devices at any given time. However, it is highly unlikely that a computer would ever use that many devices. The 127 device limit assigns addresses to each connected device so the computer can tell devices apart; if the computer erroneously assigns two USB devices the same address, it can't tell them apart. If the computer will not recognize a flash drive, try rebooting the computer and reconnecting the devices. The addresses are re-assigned on restart.
Bus-powered USB Hub Problems
The system may not be able to recognize the flash drive if the drive is connected to a bus-powered USB hub. Bus-powered USB hubs split available power between the ports; if the port doesn't have enough energy to operate a connected device, the device won't work. A bus-powered hub may reduce the power flow to less than 100 milliamps, which is insufficient to run flash drives. Try connecting the flash drive directly to one of the computer's USB ports or switching to a self-powered USB hub to access the device.
- Microsoft Legal and Corporate Affairs: ExFAT File System
- PC Magazine Encyclopedia: Definition of: Plug and Play
- Microsoft Support: Setting the Plug and Play BIOS Option (PNP OS) in CMOS Setup
- Windows Server: Enable or Disable a Plug and Play Device
- The Guardian Ask Jack Blog: How Many Devices Can I Have in a USB Tree?
- PC Magazine Encyclopedia: Definition of: USB
- PC World: How to Choose a USB Hub
- Apple Support: Apple Computers and Displays: Powering Peripherals Through USB
- PC Magazine Encyclopedia: Definition of: USB Hub
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