Solved: Drive Letters Cannot Be Assigned to Flash / USB Drives Under Windows XP

here's a screen shot showing the discontiguous mapping letters that work
for me -- they even get retained across boots.

the USB devices will get mapped (for me) as E:\ F:\ when attached

Not following ;) Whats your issue again? :)

Bluemouse's fix resolved the issue for me and I am extremely grateful to you as I had previously spent countless hours looking for a fix for this issue and your fix was the only one that worked.

I do have some comments that may be helpful to others with this issue as follows:

My machine is running Windows XP SP2 (and it was upgraded to SP2 but I don't think that is relevent to this issue). My issue was exactly as Bluemouse stated in the beginning, however, in addition, I had discovered that when I did manually assign a drive letter to the partition on the usb flashdrive, even though it was not seen in My Computer or Windows Explorer, the data on the Flashdrive could be accessed by drive letter from a command prompt. Of course, after the machine was rebooted, the drive letter went away again.

Below are some differences that I encountered on Bluemouse's fix (at least on my system):

On step 3, there was no MountedDevice1 folder, only a folder called MountedDevices. I performed step 4 on the MountedDevices folder on my machine.

On step 8, the key was called UpperFilters

----- I think deleting the UpperFilters key in step 8 was what did it on my system as I originally deleted the UpperFilters registry key as per Bluemouse's instruction and the issue was resolved. I then ran the reg file I had saved previously to put the UpperFilters registry key back because I was not sure what it did. I then experimented further and was able to narrow down the specific cause and fix the issue while still keeping the UpperFilters key in my registry ----- Here are my notes:

There were three values in the UpperFilters key in the registry on my machine as follows (and this was the order they were originally in):

snapman
PartMgr
Phylock

I found that snapman (which is a service used with Acronis True Image) was causing the issue and to be more exact, it was not that it was one of the values in the UpperFilters registry key, but rather that it was first in the list. By having snapman last in the list, I could still use that service but it did not cause any drive letter assignment issues.

This is the order they are in now and all is working well:

PartMgr
Phylock
snapman

Important Note: If you plan to leave the UpperFilters key in your registry (rather than deleting it) ,then at a minumum it needs to have the value PartMgr in it, as that value is for the Windows XP "Partition Manager Driver" (partmgr.sys) which Windows XP uses to assign drive letters to partitions.

BTW... I did try putting Phylock (is used by another imaging program called Image for Windows) first, then PartMgr, then snapman, and there were no issues, so the issue only occurred if snapman was prior to PartMgr.

I solved this problem another way round. Deleting the upperfilter I see more like a workaround. I think the upperfilter is there for a reason. Btw I don't think you have to delete the MountedDevice thing. The Bluemouse (workaround) works fine for me just deleting the upperfilter. Take a copy of the key (or better of the whole registry) before you do anything. Don't mess with the registry if you don't know what you are doing. After you have deleted the upperfilter do a reboot. After the reboot Windows should tell you it has installed some hardware and want's to reboot. Do that and you should be good. Works for me. Now, here's what I did instead of deleting the upperfilter. I found out the file SPTD.SYS in C:\windows\system32\drivers (XP) was the reason for bad behaviour. The SPTD.SYS and SPTDxxx.SYS belongs to Daemon Tools. The xxx are some numbers. So, by uninstalling Daemon Tools and rebooting, same thing happend. After reboot windows installed some hardware and after a new reboot everything was ok. If you have Daemon Tools installed, to figure out if thats the reason, move the two files mentioned above to an empty folder. Do a reboot. After the reboot windows should install some hardware. If you can see your Flash Drive after a new reboot you know the reason. I don't know who's to blame. The Daemon Tools or the Flash Drive. But there have been some problems with SPTD.SYS over time. Another thing. After doing it, no matter what solution you use, take a look at your drive letters. They maybe changed. Remap them back to where they were from the start. Sorry for my bad english.:o

Peace
Cheers

First of all, HELLO TO EVERYBODY of this GREAT community! :)

This is my first post here.

GREAT, Redwin! ;)

My problem is exactly the same posted by Bluemouse and added by JohnMart. My first try was to do what Bluemouse described, but don't work for me and I needed to restore de backuped registry because the normal boot failed after the changes.

But after to read your post, Redwin... I simply follow your words - I have Daemon Tools installed -, moving SPTD*.sys out from \windows\SYSTEM32\drivers and reboot: PERFECT! :bounce:

Just this to solve for me - the exact point! - MANY THANKS REDWIN (rep to you)! :grinthumb

PS.: Probably I'll consult this GREAT forum again in the future, but I registered just now only to post this message and to thank by the support.

SO, CONGRATULATIONS TO EVERYBODY who created, support and announce this *VERY* GOOD site! :D

I just registered to say THANKS for the solution. It worked perfectly and I am a happy man again.
:hotbounce
:bounce

In my case the USB memory stick/flash drive works if it is connected before user logon to computer, but not if it is connected after logon.
I haven't got file C:\WINDOWS\system32\drivers\SPTD.SYS and solution from BlueMouse didn't work.

Other symptoms are all the same.

1) The drive letter is assinged in the Disk Management
2) I can work with the files on it in CMD window.
3) I can open and save files in any application including IE.
4) USB Hard Drives of any kind work fine.

You migh think that there is no problem just plug it in before logon.

The problem is the system / or better say systems (96 of them in 4 computer labs) are used in a University. There are about 4000 users and itis hard to explain it to each of them.

I am looking after 11 computer labs. 7 of them are MSI Hetis (Intel 915 chipset) and they don't have problem. But 3 older with Intell 865 and new one with DQ965GF chipset are having problem above which I am trying to solve for the last 6 months (from time to time).

Note: I am using same XP Pro SP2 Syspreped image on all computers. The image orignally was developed on MSI machines but I have tried later to reinstal Windows on the 965 chipset image (on the top of existing Windows) and the problem stayed. The image is over 35 GBs mostly Engineering and programing applications whicha are updated at least every semester start, so I don't want to maintaind 2 or 3 images.

Tere is no problem with any of them when I install clean Wndows.

Any help appreciated.

I followed Bluemouse instructions and it worked for me and my camera and all my usb devices are working now. But now in My Computer I have 2 new Local Drives (E) and (F). My hard drive is C and CD-R is D, and now I have these 2 local drives. The first one is a FAT system and it contains a Dell folder and all files MDM files like "Dellsys.mdm and usbmass.mdm.. The 2nd one has a couple of folders. The folders are BAT" , "SRC1" , "SRC2" , "SRC3" , "SRC4" , "SRC5". Can someone tell me what these Local disk are and are they harmful to my computer? Do I need to put those 2 things I backed up from the Registry back there?

I tried all these solutions posted in this thread but my new mp3 player e280 still does not show as a drive letter. It does appear in the device manager and it works but in order to use automatic sync software it has to show as a drive letter. Any other ideas? THANKS!

Many thanks from Thailand.

Now figure out what caused it. Thanks bye

I've had the same issue on a dell tower running XP 2002 SP2. deleting the upperfilters (plural, btw)from 4D36E967-E325-11CE-BFC1-08002BE10318 worked great for me too. It is likely that Auto update did a downgrade to some files or stomped on a config - how pathetic is that? Microsoft should be embarrassed that everyday users have to do this crap just to get their junk OS to do everyday stuff. Do Linux/UNIX/OSX have issues routinely reading a mounted drive? answer: almost never.

I found a MUCH easier solution to this issue. I simply deleted the device from the Device Manager and rebooted. When I rebooted the drive letter was assigned to D: instead of E:. Here is exactly how I did it:

1) Right-click My Computer and choose Manage
2) Select Device Manger
3) Expand Disk Drives (make sure your SD card is inserted before you go to Device Manager)
4) Left-click on SD Memory Card and choose Uninstall
5) Reboot

Hi guys, new guy here.

Just thought I'd register to let you know another way of fixing this is similar to Redwin's idea, however it doesn't require a restart.

If you have Daemon tools installed, simply right click on the tray icon and set the amount of virtual drives to 'disabled'

worked for me, who knows.

Thank you Bluemouse!! After scouring the internet for 3 weeks this finally worked!! I backed up the registry filed like you said, and after a blue screen and a couple of reboots, I plugged in my mass storage device and WALA!! It was automatically assigned letter F; by the XP explorer!! Letter E: was assigned to a virtual drive on my Lenovo IBM, drive C:, used for backup and recovery. I suspect that there was a conflict before, with the IBM virtual drive and my USB mass storage, both trying to use the E: drive. I had tried using Disk Manager to assign another letter to the USB mass storage, but it still had not worked. Oddly enough I was able to access the USB mass storage device from the the Device Manager and other programs like Outlook for attachments, but NOT through XP Explorer. NOW it works!! Just a question: I noticed that the DOS-Drive letters were recreated in the mounted device folder.... How about the upper-filter thingy? Is that automatically re-installed as well?

Now another issue: How do I get my Plug and Play to work?? I normally wouldn't care, but I'm trying to install a Canon printer that relies on the plug n play for installation. Before I reinstalled Windows XP, I used to get a "New Hardware Detected". Not any more. Anybody??

Just some additional info/suggestions for anyone else finding their way to this thread...

There are several different methods to fix problems caused by "Driver Letter Conflicts" (which is typically the root cause of the problem described in this thread)

IMHO: The simplest (and most thorough) solution is using the DriveCleanup Tool

The "Drive Letter Conflict" occurs because your USB device is competing for the drive letter with some old / prior installation data still on your computer.
And your USB device has lost the battle for the drive letter! (so the USB device appears in Device Manager but not My Computer or Explorer with a drive letter)
Running the DriveCleanup Tool will uninstall / remove old installation data for all currently unplugged USB storage devices
So the next time you replug the USB storage device, Windows does a new, clean install and reassigns it the next available drive letter


Here's some helpful links for reference
> See this post for How to use the DriveCleanupTool
> If you're still having USB issues see Troubleshoot: Windows Won't Recognize Your USB Hard Drive (<= rewritten 11/21/09. So if you've read this post before is worth taking another look!)
> To help avoid problems in the future see How to Avoid Problems with USB Storage Devices