Windows 7 does not detect multiple External Hard Drives

Anonymous
2009-11-29T15:20:15+00:00

I have recently purchased a HP Pavilion laptop Winndows 7 Home Premium. I have two 500 GB external Hard Drives. When I connect them individually to the system, they are recognized and I can copy files from/to to these external Drives. But when I try to connect both at the same time, Windows 7 does not detect the drive I connect second. Any help is greatly appreciated.

Windows for home | Previous Windows versions | Devices and drivers

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Anonymous
2010-02-27T18:33:22+00:00

If you are still having the problem detecting the 2nd external hard drive, then I would like to share with you that I have also experienced the same problem when I tried to connect 3 external Seagates 500Gigs each, and each of the HDs with their own power supply.I would like to also share with you, if you are still having the problem, that I have been able to connect and my Windows 7 Pro has been able to detect all 3 external HDs and each drive has its own letter assigned to it.Each external drive (ED) is accessible like if nothing ever happened.The issue seems to be a conflict of IDs assigned to each (ED) when we connect an (ED), then when we connect a 2nd (ED), then the 2nd (ED) is trying to use an ID that has already been assigned to the 1st (ED), therefore, the 2nd (ED) stays "offline" to avoid a conflict with the 1st (ED).The technical term is "The disk is offline because it has a signature collision with another disk that is online"To make the 2nd and 3rd, and 4th (ED) to be online, then you have to go to:- Computer Management- Disk Management- Scroll down so you can see your external drives- You will notice that the 1st (ED) is "Online"- You will notice that the other (EDs) are "Offline"- Right-Click on "Offline" and a shortcut menu will give the option to turn (ED) "Online"- Wait for a few seconds and now that (ED) will become available to be used.I hope these findings will help you guys minimize your frustrations as I had them before I found this solution.

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Anonymous
2009-11-29T16:49:05+00:00

If the drives are powered by the USB bus and do not have their own external power supplies the problem is that the laptop is not supplying sufficient USB power to drive both.

The USB specification is that each port should supply 500mA at 5V. To conserve their batteries, laptops usually provide 500mA to be shared between all the available ports. If you need to use several USB devices with significant power requirements you need either an external powered USB hub or to provide the devices with their own power supplies.

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  1. Anonymous
    2011-08-08T18:15:10+00:00

    Does making the disk online change the ID? Does this have to be done every time you mount the "bad" drive?  Is there any chance the two drives will get confused?

     I have seen another response that uses diskpart to make the "bad" drive some unique id so this never happens.  Not sure which way to go, making the drive online is the simplest but I want to avoid future issues.

    this is a pocket drive so it gets connected/disconnect often.

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  2. Anonymous
    2011-07-14T19:12:20+00:00

    Thank you. :D This was exactly what was wrong for me. I have two iOmega eGo 2TB HDDs and I wasn't able to get both to show at the same time.

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  3. Anonymous
    2011-07-07T20:28:11+00:00

    easiest and actual solution is:

    1. Open Command Prompt.
    2. type DISKPART - a new window will open.
    3. enter command : LIST DISK. This will show you all the connected disk with the offline one.
    4. Now select the offline disk using the next command SELECT DISK <disk_no> wheredisk_no is the offline disk number which you can get from step 3 result.
    5. Now you have selected the offline disk. Now enter command ONLINE DISK.

     

    and BOOM, your disk is available in my computer, if not then or you are getting any error please contact me @my blog...

     

    Thanks

    I have 4 external drives which i hook up to my laptop via a USB hub and I'm running Windows 7 Ultimate. Randomly, one of the drives will not show up in Windows Explorer or in Disk Management. Even though all the drives work perfectly fine.

    ABHINABA_BASU's suggestion worked perfectly.

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