That would work
You system is trying to boot to the USB hard drive it sees (your Droid)
You can check your BIOS boot options to see if you can set USB boot or USB boot priority to disable or remove the droid as a boot device.
(I don't know if these options are advaiable in the desktop boards)
When a USB device is detected, the BIOS puts it into the boot order. (usually as the first boot device)
If you remove the USB device, it get removed.
When you connect it again , it is detected as a new device and goes back into the boot order.
Disabling USB boot or USB boot priority will fix this . (of course if you do want to boot to a USB device in the future, you need to re-enable it.