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Recently my Dell Studio 1550 laptop running Windows 7 x64 has started having problems with USB devices. I have two devices I typically connect: a Western Digital external HD and a SanDisk compact flash reader. Up until a few days ago, I could have both connected and they operated normally. Now, when I try connect both whichever is the SECOND device plugged in fails in a variety of ways. The order does not matter; the first device works and the second device always fails. The error message is usually "Windows does not recognize this USB device." or "Device driver software was not successfully installed." Sometimes it will appear under "My Computer" but attempts to access it cause Windows Explorer to hang. Anyone have an idea about what could be wrong?


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This sounds like one of those old IRQ conflicts. I can't really say what the problem may be, but perhaps USB driver problems are to blame? – bwDraco Jun 10 '11 at 18:14
This has all been complicated by the fact that it magically just started working again. – Scott Jun 10 '11 at 20:11
up vote 3 down vote accepted

I have never come across this, but, if you are getting the same in all sockets I would attempt a guess at a bad USB driver upgrade.

Try taking a look in Reliability Monitor (Click the Start Orb and start typing Reliability (only need first few letters) and View Reliability History should pop up - click on it)

From here, take a look over the last few days / since you noticed the problem starting and see if there have been any USB driver (or similar related) updates that have happened.

... Even Windows updates may have affected USB functionality, you can either attempt to see the release notes or manually update them.

If it hasn't and manually updating drivers doesn't work - I am out of ideas other than to say if no updates have occured, it could be hardware failure. (Although, a reinstall of Windows should be done just to guarantee it is failure).

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And again with the great answers that I was about to say... GOSH @WIL! Stop being so smart... Great answer! +1 – David Jun 10 '11 at 18:12
Thanks, I had no idea Reliability Monitor even existed! No updates were applied since it was last working (other than virus definition updates). – Scott Jun 10 '11 at 20:13
It's been so inconsistent I think 'hardware problem' is the most likely answer. – Scott Jun 13 '11 at 13:52

It is possible that your laptop is not providing enough power via USB to support both devices under load. An possible test/solution is to get your hands on a self-powered USB hub and see if your problem resolves itself.

Another possible problem is that windows might be attempting to assign the same or overlapping drive letters to the devices. If the drive letter assignment doesn't matter to you or your software, you can try manually assigning a new drive letter perhaps 5 or more letters further down the alphabet. See ( ) for information about changing drive letters.

(Note that I would caution you against changing the drive letters of the internal hard drive(s).)

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I thought power might be an issue, though the external HD has it's own power supply. The self-powered USB hub is a good idea, I'll try it thanks. – Scott Jun 10 '11 at 20:06

I experience the same problem, where only the first USB HDD being connected can be accessed via Windows Explorer, the second one is not shown at all and no error message is displayed by the system. This behavior is the same no matter where I connect the USB HDD, directly to the laptop or indirectly via an external USB hub (self powered or not).

However, something to notice is that on "Devices and Printers" both USB HDD are shown, for whose I can obtain properties, but only one allows for more actions such as "browse contents", etc.

On top of all that, the Device Manager window always shows both USB HDD under "Disk drives", but only the first one connected under "Storage Volumes".

I was going around to different sites and search engines but nothing can confirm if this is an expected behavior for software/hardware or a bug of some kind.


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