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USB removable memory not accessible in explorer(or given drive letter)

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Old 10-27-2006, 09:23 PM
DemanPhos Offline
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Join Date: Oct 2006
Posts: 12
USB removable memory not accessible in explorer(or given drive letter)

System: XP Pro Version 2002 ServiceP 2
Running soft firewall (Sygate), ATI tray.
Four partitions on a single HD - EXT3(logical1 - part 0 - not mounted), SWAP(logical2 - part 0 - not mounted), NTFS(C drive - part 2), NTFS(H drive - part 3 - windows system). Second HD (K drive), one part FAT32

The XP install is on the H partition, which is roughly 25GB, with the C part being about 45GB.

Hardware: AMD Athlon 64 3200+ (single core) 1GHz ' 1GB RAM PC3200-2stick256 PC2100-1stick512 ' ATI AGP RADEON 9600 128MB ' Gigabyte mobo with onboard LAN being used ' 4 port USB mobo back hub, 2 port USB case front hub

The USB drivers/controllers were ULi, but I uninstalled them for the generic windows drivers/controllers.

Problem: When plugging a removable storage device (iPod, flash stick, anything) into one of the USB ports, Windows recognizes there is a removable storage device, identifies it, uses an appropriate driver, but does not assign a drive letter. When I manually assign a drive letter to the removable disk it does not 'show up' in My Computer, nor can I use the drive letter in Explorer to access the mounted disk. I can, however, use DOS to access the mounted disk normally, but no other method.
Changing the USB port causes no difference. Changing the USB HUB controller/drivers from mobo specced to generic caused no difference. Manually assigning different drive letters to the storage device caused no difference. Using different storage devices(an iPod, three different flash sticks) caused no difference.

Possiblilities proposed:
*Windows craps out because it can't handle the partition/drive configurations, and sits on it's proverbial hands.
*Explorer doesn't update it's knowledge of the drive even when it's assigned a letter manually, and thus doesn't know what the user is talking about when I ask it to access that letter. DOS just happens to know better than Explorer.
*My USB/mobo driver/controllers are messed up, and thus is confusing Explorer into thinking it can't access the drive, while DOS somehow sidesteps that problem.
*I've disabled or set to manual a service thatis required to access a removable/USB storage device. Very possible. A list/reference of what services perform what tasks (especially in regards to storage, usb, plugNplay) is appreciated.
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Old 10-31-2006, 01:50 PM
DemanPhos Offline
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Any ideas? Any at all?
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Old 11-03-2006, 08:29 PM
royorlev Offline
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Join Date: Nov 2006
Posts: 1
solution: a damaged virtual cd driver

I think i have a solution for this problem.

I had the same problem and looked around the internet for a solution, but nothing solved my problem. All the answers suggested testing the usb stick on another computer or using the disk management to assign a new drive letter, but these procedures didn't solve my problem.

I had Daemon tools (virtual CD) previously installed on my system, and the installation was corrupted. I think it was after i repaired windows using the repair procedure from the original CD, which actually installs windows again over the existing one. After that Daemon Tools stopped working, disappeared from the "add/remove programs" list, but somehow stayed on the system and caused trouble...

I think what was causing the problem is not Daemon tools itself (i used ver 4.0.3), but the ScsiPassThrough-driver (SPTD) that is installed with it (ver 1.25). Someohow it confuses windows with the drive letters. (according to daemon tools "SPTD is also used in some proprietary security, antivirus and monitoring applications...") so maybe you could have the same problem even if you don't have daemon tools installed. Anyway, you may want to try these steps anyway, they might solve your problem.

i couldn't re-install daemon tools, since i got error when installing the sptd driver.

How to fix the problem:

1. download the stand-alone sptd driver from here:
or here for 64bit:
do not run the installation, but save it to the hard drive.

2. start the computer in safe mode.

3. click start->run... browse and select the installer from where you saved it, and add the word remove at the end of the line (so you will have something like (in my case i placed the installer on the desktop):
"C:\Documents and Settings\User01\Desktop\sptdinst_x86.exe" remove
and click ok.

restart the computer normally.
After i did this, i plugged in the usb stick and VIOLA! it works!

You should be able to reinstall daemon tools if you wish to. If you still have problems with installing it, restart the computer again to safe mode and do the following:

4. repeat step 3 but change the word "remove" to "add" like this:
"C:\Documents and Settings\User01\Desktop\sptdinst_x86.exe" add
and click ok.

5. restart again normally and install daemon tools.

I hope it helps...
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Old 11-06-2006, 05:00 PM
DemanPhos Offline
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Join Date: Oct 2006
Posts: 12
royorlev, you were correct. It was the SPTD service, apparently. I did what you said, but it refused to do anything in safe mode. When I restarted I just used the installer and it gave the option of automatically uninstalling it, so I used that.

Sad, but I'll just have to use old versions of Alcohol and Daemon Tools.

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Old 11-08-2006, 11:39 PM
torpedomax Offline
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Join Date: Nov 2006
Posts: 1
WOW that worked perfectly for my situation

I upgraded from XP home to XP pro.(no this does not require a reinstall of windows XP there is a utility that will do it) in the process a few programs got hit pritty hard including my APC UPS detector and daemon tools.

I had the same symptoms listed above plus a few more. if I inserted any USB mass storage device it would apear under device manager however a drive letter would not be assigned to it. if I then loged out of that account and loged back in I would then see the usb device on the assigend drive leter. I could use it as a normal device however this was a pain and would break promptly after being removed (it would also not free up the drive letter till reboot.) I was also able to access the device throu device manager by tight clicking and the clicking open.(this was not 100%) I stumbled onto this web site and ran the command line and POOF... it all works again. a mighty simple fix for what seemed to be a larger problem.

Thank you, you are my hero for the day
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Old 11-09-2006, 05:33 AM
xodia Offline
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Posts: 2
that would sound right to me... i have never heard of this before but if there was a corrupted install then that could be the culprit i suppose
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Old 11-28-2006, 03:00 PM
hitm4n Offline
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Posts: 1
Just wanted to say a BIG THANKS to Royorlev. I trawled the web for fixes for this issue and this was the solution.

Another solution was to delete all the installed usb devices from the registry and allow them to be reinstalled. That didn't work.

Another was to try mem stick on another pc. Mem stick was fine on other PC so that got me nowhere.

Another was to reformat the drive on another PC. I did this and still it failed to appear on my home pc.

Another was to switch drive letters around. Use something never used before. I tried 3 diff letters at both ends of alphabet. That didn't work.

I downloaded that SPTD install file, went to safe mode and ran it with remove, rebooted and plugged in the mem stick and hey prestoroony, G: was open on my desktop in half a second.

Many many thanks.

p.s. the above links to the install files failed for me, i had to go to to find the installs.

Happy 1gig USB stick user
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Old 01-02-2007, 04:34 AM
neuwirthe Offline
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Join Date: Jan 2007
Posts: 1
no need to remove

The duplexsecure site has the following instructions for disabling SPTD without removing it. I followed these instructions and then I saw my USB sticks again in explorer. I have no idea which software installed it, I do not have daemon tool installed.

A: If your system has some problems with SPTD installation you can do as follows:

If your system is already running then go to step 2 directly. Otherwise start from step 1.
Step 1. Boot in safe mode and press ESC key when you see on bottom line of display: "Press ESC to cancel loading SPTD.sys". This will abort loading of SPTD layer.
Step 2. Find "HKEY_LOCAL_MACHINE\System\CurrentControlSet\ Services\sptd" registry key in REGEDIT and set DWORD Start value to 4 (i.e. disabled).
Step 3. Reboot again in normal mode and check if your issue is solved.

To reenable SPTD restore the DWORD Start value back to '0' and reboot your computer.
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Old 02-07-2007, 02:44 AM
wilkoa Offline
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Join Date: Feb 2007
Posts: 1
Great advice

Just wanted to say thanks. This problem has been driving me nuts.

I used the regedit solution posted and this worked fine for me.

Great thread
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Old 02-11-2007, 08:34 PM
Alcohol Hater Offline
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Join Date: Feb 2007
Posts: 1
Still a problem!

I've been having the exact same problems. Whenever I try to access my usb flash drives, ipod, etc., my computer gives me a message which reads...
X:\ is not accessible. Access is denied
As I've read Alcohol 120% seems to the same thing as Daemon Tools does. I installed Alcohol a while ago, but since then I've upgraded to Windows XP SP2. I believe that is when the problem first started.

So far I've tried both the SPTD and the registry editor solutions and the only positive result achieved so far was windows asking me to open my flash drive... but only once. I unplugged the flash drive, then plugged it back in, but it seemed to relapse back into its stubborn inaccessible mode. I've also tried repeating the removing of the SPTD and I haven't connected since. Perhaps I should've left it plugged in and restarted the computer or something before I disconnect it? Also, since the solution doesn't seem to be working after the first try, is there any way I can reset the settings and start from the beginning?

Thanks for the solution posted anyway. Any more help would be much obliged.
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Old 03-14-2007, 12:06 AM
loopyloon Offline
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Posts: 1
royorlev's solution is right on the money for me. If you installed any type of CDROM emulator before, it is a very probably cause.
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Old 03-19-2007, 10:02 PM
DavidESharpe Offline
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Join Date: Mar 2007
Posts: 1
doesnt work for me

i have the same issue except i can't access any drivae that Isn't my main hard drive. I have since split that into two partitions C: and E: and i can access both of those, but not my A: D: or any any other. I didn have Alchohol120% but have i uninstalled it and cant find any SPTD in the registry. This is really beginning to be a bugbear for me, and may have to wipe windows and start again, but REALLY dont want to have to reinstall everything on my machine again, that's gonna take days
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Old 03-24-2007, 07:42 PM
turbulent Offline
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Join Date: Mar 2007
Posts: 1
the needle in the haystack

a virus scrambled my daughters laptop - after four days of repair installs, replacing software, firewalls antivirus etc etc etc etc, XP would not assign USB drive letters, I suspected that after Daemon tools had been damaged by the virus that somehow the drive letter assigning mechanism had become constipated but I didn't know how and searched the internet wilderness for another few days banging my head on various solutions - none of which worked (how do we rid the net of parrot syndrome) until I read royorlev's post. I downloaded SPTDinst-v142-x86.exe from (note newer version now available royorlev's link now dead) and it fixed the problem. the exe ran fine in windows without safe mode or using command line. Anyway royorlev is my current hero - many thanks!
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Old 03-28-2007, 04:20 PM
djx_xx69 Offline
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my name is roy too!

and these steps worked for me
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Old 08-22-2007, 07:34 AM
eivanov Offline
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Join Date: Aug 2007
Posts: 2
I had to repair an XP Home installation which would not attribute a letter to inserted usb flash drives or digital cameras. I could see the sptd service in the registry, the regedit+reboot trick worked fine for that machine. I don't where that service got installed from, though.

Many thanks to royorlev and neuwirthe,
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