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When I connect my external hard drive to my PC, it tries to boot from it but is unable to do so because there is no OS installed. And rightly so, I only want to use it for dumb storage.

How can I set it so that it's not bootable? I regularly boot from other USB drives, so I don't want to change my boot order in the BIOS.

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it's impossible . you configured your pc to boot from USB and when you connect hard drive to USB, your pc must check it and ... – hamed Mar 29 '13 at 8:19
Change boot order in BIOS – pratnala Mar 29 '13 at 8:27
I've got two other hard drives connected, and the PC doesn't try to boot off them, just this third one. The new one has an MBR - I guess I want to know how to remove the MBR from this hard disk – Ace Mar 29 '13 at 8:28

Modern BIOSes generally move on to the next device in the list according to the boot order specified, if the previous device is not bootable. If that's not happening here, use diskpart or GParted to ensure the USB HDD's partition is not set to be active. For diskpart follow the steps below but use the inactive command instead as shown by the command's help screen (take care to select the proper disk and partition!):


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Thanks Karan. Tried this, but the partition was already inactive. Set it to active, then inactive again, but still having the problem. – Ace Mar 29 '13 at 8:41
How many partitions does the USB drive have? Did you select the proper partition? Can you add a screenshot of Disk Management to show the partition map of the drive? If you correctly set the partition to inactive the BIOS shouldn't try to boot from it, so what happens exactly? Does the PC just get stuck after failing to boot from the drive? Any errors displayed? – Karan Mar 29 '13 at 8:45
The drive has only one partition. Here's a screenshot of diskpart, and here's one of EaseUS partition manager. What happens when I boot is after the initial BIOS info, it shows a blinking cursor on a blank screen and stays there forever. This is at the point where the bootloader is shown if the external HDD is not connected. Again, thanks for your help so far. – Ace Mar 29 '13 at 8:57
How old is your PC? I've seen old BIOSes behaving this way, whereas like I said above newer ones tend to move on to the next bootable device. If it's a BIOS limitation and no update exists, the only option left to you might be to change your boot order after all. – Karan Mar 29 '13 at 9:03
It's a two year old laptop (i5). I have two other hard drives connected which don't cause this problem. If you see the second screenshot I posted, EaseUS partition manager says that there is an MBR on the disk.. – Ace Mar 29 '13 at 9:16

If you don't want to change your BIOS boot order then try this simple thing. While your computer is about to boot, keep Pressing Boot Menu key(i.e. before it detects boot devices itself). Boot Menu key defers as per computer manufacturers. it's normally F8 or f10 (mostly function keys) or ESC. If you do this with perfect timing, you will get one Boot menu asking you to select Which Device to boot from. Select your PC's internal HDD.

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