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I've got 3 hard drives (with power supply, USB 2.0 and 3.0). They are all recognized by Windows7 x64 when they're plugged in individually, or when 2 of them are plugged in at the same time (on any of my 4 laptop's USB ports).

However, when the 3 of them are plugged in at the same, W7 only detects the 2 first ones plugged in.

I also tried to plug them on a hub (which has a power supply) and it gives the same result.

When the 3 of them are plugged in at the same time and there's 1 or more pen drives plugged in, only 2 hard drives are recognized but all the pen drives are recognized as well...

Anyone might have a clue why that's happening?

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migrated from stackoverflow.com Jan 12 '12 at 1:56

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this is more of a super user question. but i would guess that the third is underpowered. –  madmik3 Jan 12 '12 at 1:17
    
All three are powered? –  Paul Jan 12 '12 at 2:30
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definitely not power supply, it was just an "a signature collision with another disk": other usefull link social.technet.microsoft.com/Forums/en-US/w7itprohardware/… –  user1144446 Jan 12 '12 at 22:49
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1 Answer 1

up vote 1 down vote accepted

1) This question would definitely have been better on superuser.com. Live and learn :)

2) This link has two good suggestions:

http://answers.microsoft.com/en-us/windows/forum/windows_7-hardware/windows-7-not-recognizing-two-usb-external-hard/740fcde9-b000-4c49-9a43-c0926b37feb7

a) power supply

 ... and/or ...

b) Manually enable the (third) drive in Disk Mgr (where it might be visible, to enable)

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