Ever had a problem connecting 2 "identical" external HDDs?

If you have ever connected 2 identical ext HDDs and found both work fine independently but not when both plugged in.
Then you may have this unusual problem I just struck.
Bought WD Elements 500GB as a present 3 months ago.
Bought another on special recently.

Whenever one is plugged in first works fine. Second one is not assigned a letter and offline. Reverse the disks and the same applies.

Both where manufactured with the same disk signature!!!!
Changing the disk signature of one solved the problem.

Possible driver signature problem. Look in storage devices for an error, maybe

Interesting, mj.

Windows is supposed to do that for you.

Perhaps it doesn't if they are both usb connected.

SIW2 said:

Interesting, mj.

Windows is supposed to do that for you.

Perhaps it doesn't if they are both usb connected.

Yes that also puzzled me about Windows not automatically changing one.

It was a long shot - I looked at the MBR of the disks with a Hex editor and couldn't believe it.

What about the poor soul that just wants to plug them in and work!