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
    2010-09-15T19:05:07+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

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  2. Anonymous
    2010-12-04T06:55:10+00:00

    Actually, nobody is retarded (unless it's you).  The solution offered by Win7Survivor worked exactly for me. Just make sure you right click on the left side of the box.  Quick and easy.  This may not work for everyone.  You may have to try the command prompt fix then.

    This problem occurs when two hard drives end up with the same signature (identifier) like when you clone a drive.

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  3. Anonymous
    2010-09-09T02:06:28+00:00

    Ok to Win7Survivor:

    If it were as simple as turning a drive from OFFLINE to ONLINE (which it doesn't) noone would have any problems.

    It doesn't give you that option, the disk that has the signature collision issue will show as "disk offline" with no right-click option to change to online.

    I'm using Windows 7 Ultimate and (2) 2TB WD My Book Essentials HDD's. And for the others that think its a power issue, you can have 3 different types 

    of external hdd's (with its own power supplies and it works fine -- they just can't be the same exact make/model). And for those that have looked into

    the "diskpart trick" from the command prompt, that does not work either (I've tried).

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