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How to troubleshoot unrecognized USB sticks?

Nov 7, 2013

Track down USB hardware problems and software conflicts.

The USB stick has been plugged in, the drivers are being installed and Windows is making all kinds of funny sounds signaling its apparent recognition – or are they? After the initial stir has settled, one more often than not finds nothing but blank white space where the USB drive should be in Windows explorer. The reasons for this problem are typically manifold and can be rooted in both hardware and software. Here's how to narrow down the cause systematically.

Hardware-related problems:

1. Broken cables (in the case of USB hard drives)

Obviously, this may sound fairly trivial, but its always worth taking a look at the USB cables, as they might be faulty, bent or even just loose. This particularly applies to older models that have been in the line of duty for some years. Alternatively, an USB extension cable can also be to blame, as some USB devices outright refuse to work with them. Try using a different cable or, if possible, try plugging the device directly into one of your USB PC ports to eliminate cables as the suspect altogether.

2. Overloaded internal USB hubs

Most peripheral USB devices draw their power directly from the USB port of your PC and need no additional power cable. Fairly often however, the internal USB hubs might be designed to bite off more than they can possibly chew, leading to power fluctuations whenever too many USB devices are plugged in next to each other. To find out whether or not this is the cause, try unplugging some of them and see if this solves your problem. If so, its probably a good idea to see if you can spread out your USB devices permanently and connect them to other USB hubs, ideally in a way the separates your more demanding gadgets such as external disk drives (often exceeding the 500 mA power limit of USB 2.0) from the smaller ones.

3. Underpowered external USB hubs

Conversely, if you are using an external USB hub to power your devices, you might want to check if it is sufficiently powered. In many cases, these require an independent power connection to an electrical socket or are equipped with multiple USB plugs that are easily mistaken for spare connections to compensate for their increased power demand. As above, if you suspect this to be part of the problem, try checking all corresponding cables.

Software-related problems:

1. Faulty drivers

This is the probably the biggest elephant in the room concerning missing USB sticks. Luckily, the responsible drivers are just as easy to delete as they are to reinstall, so resetting them is always worth a shot.

First, make sure to unplug your USB stick from your PC. Then, open up your device manager by holding down the Windows key + R and entering “devmgmt.msc”. Locate your USB ports by expanding the entry “Universal Serial Bus” (typically at the very bottom of the list). Check if there's a yellow exclamation mark next to one of the entries, as this suggests issues with the installed driver.

You can reinstalling it by right-clicking on its name and selecting “Uninstall”. After the device has been removed from the list, click on the button “Scan for Hardware Changes” in the menu bar at the top to give Windows a gentle bump, thus starting the installation process. After the process has finished, try reconnecting the stick and see if that has helped your cause.

Tip: You can even monitor the power draw of each individual USB hub and all connected devices by double-clicking an entry in the device manager and switching to the tab “Power”. The field “Hub information” at the top of the window will tell you how much power the port supports in total, while the field “Attached Devices” at the bottom will give you an idea of how much of it is actually used by devices.

2. Interfering filter drivers

While the bulk of USB functionality is handled by the “main” drivers in the device manager, there might also be lesser known “filter” drivers installed on your system to complement them. These take a supporting role in coordinating the devices of your PC and merely add specific (and optional) features to an already existing driver foundation. Unfortunately, in the worst case they might backfire and meddle with the display of drive letters of your PC, thus causing USB devices to vanish or prevent them from appearing in the first place.

To remove redundant filter drivers, head into your Control Panel and open the menu “Programs and Features”. If you already know which program is to blame, select it and click on “Uninstall” If not, try to remember whether or not you installed any USB-related software after setting your PC up or look for the name of your mainboard manufacturer in some combination with “USB” in the software list. If you are certain to have a found the right program, delete it.

Tip: It might also help to navigate to C:\Windows\System32\Drivers and to delete the files SPTD.sys, dtscsi.sys, secdrv.sys, spdt.sys, sptd****.sys, SPTD****.sys (replace the asterisks with a number with four digits) if they are present in the folder.

3. Blocked drive letters

This is as simple as it sounds: If you have used your USB stick on your home PC before, you might have assigned a specific drive letter to it (such as E:). By plugging this stick into another PC for which E: is already occupied by some other device, your stick might fail to be recognized - particularly on older system like Windows XP. Fortunately, this issue can be resoved without much difficulty.

Method 1:

The easiest way to achieve that is to make Windows assign a new letter to your USB stick automatically. Open your command prompt by typing "cmd“ into your Windows search field, right-click it and select “Run as Administrator”. Type “diskpart” into the prompt and hit enter. This will likely open a new command prompt for the program Diskpart, in the same style as the last one. Next, write “automount enable” and hit enter again. Once the automount feature has been enabled, exit both command prompts and try plugging in your USB stick again.

Method 2:

You may also assign a new inherent drive letter to your USB stick manually. To do so, hold down the Windows key + R and enter “compmgmt.msc” into the empty prompt. Select “Storage”, followed by “Disk Management”. This will give you a clear overview of all drives and partitions that can be accessed by your PC. Thus, if your USB stick isn't faulty, it should appear in this list - duplicate drive letters or not. Once found, right-click it and select “Change Drive Letter and Paths”. This will give you three options: Add, Change or Remove a drive letter. Select whichever (of the first two) applies to you and set the drive letter to something that isn't yet occupied.

Tip: If you keep having trouble with a particular USB stick, its probably a good idea to check its data integrity to avoid the loss of data.