How can I boot from an external hard drive?

Question

How can I boot from an external hard drive?

hp

Solution 1

You need to enter the BIOS of your computer and select USB as first boot device.

Very often, the BIOS is entered by pressing a key at the very beginning of the boot sequence, right after having powered the computer on:

• F1
• F2
• ESC
• DEL
• SUPPR (on French keyboards)
• (refer to the documentation of your sytem...)

Once you're in the BIOS, you can configure the boot order: for instance try to boot from floppy first, then cdrom/dvdrom, then hard-drive... The boot order is stored in the BIOS remains the same every time the computer starts.

As suggested in other answers and comments, some BIOS allow you to press a key (F12 for instance) that will bring you a one shot boot menu: the purpose of this menu is to let you exceptionally boot from another device.

If you exceptionally want to boot from an USB hard-drive, you're likely to want to bring the boot menu up. If you want to always boot from an USB hard-drive that remains plugged to your computer you're likely to change the boot order in your BIOS.

Solution 2

or open the boot device menu (most manufacturers use F12 during the POST screen, others may use ESC or a combination) and choose the device you want to from.

Comments

[Gregory Pakosz]

works for DELL computers only?

[quack quixote]

@gregory pakosz: nah, plenty of BIOSes include a boot device menu. not all are accessed with F12; check your system documentation.

[Gregory Pakosz]

that's what i meant

[Admin]

well, i'd say, F12 is more commonly used as key to bring up the boot selection menu than ESC.

[Admin]

and as i happen to know from experience, setting 'Boot from USB' as first choice does NOT always work, the Boot Selection Menu does.

[Mokubai]

+1 Confirmed. This is also the case for my machine, a custom build with an Asus A8R32 Mobo, my BIOS has a "Press F8 to open BBS Menu" warning which brings up the Boot Device Selection screen. This is much more useful than permanently changing the boot device as my BIOS gets more than a bit stupid when bios configured boot devices vanish.

[Gregory Pakosz]

I took the liberty to edit and give a more elaborate answer after having read the opinions in other comments

[ralford]

Great summary Gregory. Though it may be obvious to some of us, this is all true after the external hard drive has already been made bootable with the proper boot and/or system files. In other words, a drive previously used for storage purposes only (that does not have boot/system files) is not yet bootable.

[NaV]

How much space does Boot-able section used if anyone wants it on Storage Disk ?

[Arash]

how we can do it using external HDD? i wander if you can help me.i need to use HDD for installing windows