USB Storage Issue in Windows XP In Windows operating system especially Windows XP, when plug in external USB or FireWire mass storage device, the drive is not been assigned a drive letter by the system, hence the USB drive or FireWire drive is not showing in Explorer and no AutoPlay or AutoRun window pops up, although the device has been detected, in Safely Remove Hardware (show device but with no drive letter) wizard. The cause is probably due to ’stupid’ behavior of XP where it won’t find an available letter from free letters pool when the USB or FireWire external drive which has previously mounted and assigned a drive letter is been inserted to computer USB or FireWire port again, but that previously allocated drive letter has been taken up and used by another storage devices. Solution: Assigning drive letter using “Change Drive Letter and Paths.” Option in Disk Management Console may not work in all cases. The workaround is to delete the registry key that represent the drive letter that has been previously assigned to the mounted USB or FireWire portable mobile flash or hard disk drive so that when the storage device is plugged in again, the whole drive letter assignment will be start from fresh, and clean. 1. Login with Administrative privileges. 2. Disconnect all USB or FireWire storage devices. 3. Open Registry Editor and navigate to the following registry key: HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices 4. Under HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices there will be registry keys with the name that resembles the format of \DosDevice\X: where X can be any alphabet letter which corresponding to your physical system drive letter. 5. Delete the DosDevice\X: registry keys that represent any USB or FireWire storages devices connected on the system before. 6. Now insert and plug in the USB or FireWire device into the port again. The drive letter for the USB and FireWire should now appear and you can use the drive normally again. Please Note: Please do a backup by exporting the registry key MountedDevices. The delete all possible USB drives, FireWire drives and external drives which have drive letter temporarily only when inserted in the system, and DO NOT delete any of the fixed hard disk drives or CD/DVD optical drives registry values. Exclude \DosDevice\A: which normally reserved for floppy disk drives.