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

Locked Question. This question was migrated from the Microsoft Support Community. You can vote on whether it's helpful, but you can't add comments or replies or follow the question.

0 comments
Answer accepted by question author
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.

Was this answer helpful?

30+ people found this answer helpful.
0 comments
Answer accepted by question author
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.

Was this answer helpful?

3 people found this answer helpful.
0 comments

62 additional answers

Sort by: Most helpful
Most helpful Newest Oldest
  1. Anonymous
    2010-06-09T06:46:47+00:00

    Win7Survivor--thanks for the info! It worked perfectly for me, Windows 7 Professional. Connected a second Hitachi 500gb drive identical to my main drive, which was cloned from it. Duh--of course the disk signature was the same. Didn't know how to fix it until your post.

    Was this answer helpful?

    0 comments
  2. Anonymous
    2010-05-17T18:13:43+00:00

    I also have the problem but I'm trying to connect only one500gig and the computer does not recognize it

    When I go to disk management it is there,   but I can do nothing with it  when I try to assign it a letter I get the following message....OPERATION FAILED, DISK MANAGEMENT IS NOT UP TO DATE.

    now what how do I get it upto date??????

    very frustrated as all my backup info from other computer is on there

    Was this answer helpful?

    0 comments
  3. Anonymous
    2010-04-30T12:28:23+00:00

    I have this same problem, "I have.......Winndows 7 Home Premium. I have two 500 GB external Hard Drives. When I connect then 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."

    However the second drive when connected is only viewable on the right side taskbar area under the "Safely Remove Hardware" icon. It is not visible under Windows Explorer or "**Disk Management"**so the Win7Survivor fix will not work. I need to be able to see it under Disk Management to change the drive letter and do not see it there.

    I assume there are drive letter conflicts. They both work fine when connected independently just not together. I tried "add a device" and that did not work.

    Thanks

    David

    Was this answer helpful?

    0 comments