An external hard drive that is bootable is a very handy tool...
There are a couple of ways to use an external hard drive
as an Emergency Bootable device, or ERD (Emergency Repair Disk).
One way is to use an image of an older install and clean it up, that is uninstall everything you don't need from the install when it was on your hard drive. The problem with this solution is that it may BSOD (Blue Screen Of Death) when you connect it to another computer due to the drivers being for the specific installation of the original computer.
Also your computer has to be new enough that the BIOS recognizes a bootable USB
Another way is to disconnect your internal hard drive(s) and then install the Operating System on your external hard drive, then again the install will have the specific drivers for your hardware and may BSOD on a different computer.
You can take an ISO image of a ERD CD/DVD and create an image that can be put on a hard drive, this would be a better solution how ever converting the ISO CD/DVD image gets a little more involved than most people want to do.
I have two bootable external drives, one has the old ERD Commander, the other has a newer Windows 7 ERD for the boot OS, both took me some time, frustrations, and finagling to get them to work.
Also not an easy task.
The easiest way to make a bootable external hard drive is with DOS. I know 'DOS is dead' but in reality it is still the fastest, smallest, and
a free Operating System you can get. Then you say but DOS will not see a very large hard drive. Not true it will see all hard drives if you add the necessary utilities to the
If you use DOS as your OS of choice you will need to use DOS ver 7 or above. (This version came with Windows 98 and Windows ME)
- DOS ver 7 has the ability to see Tetra Byte drives, I only have 1 TB drives so can't tell you where the limit is but it does see them.
- To see NTFS drives you need to load a utility for NTFS drives (NTFSDOS.EXE
you can find it with a search).
- Before DOS 6 you will need to load an IDE hard drive driver.
- And if you need CD/DVD support you will need CD/DVD drivers.
Or you could use the BARTPE or
Ultimate Boot CD
(web site removed) for Windows
XP or older Operating Systems to make your
There are a few other authors that have created bootable CD/DVD solutions that can be converted to an
external hard drive for emergency repair.
Troubleshoot, repair, maintain, upgrade & secure...
Personally I like ERD Commander because it has built in support for most tools, once you have the hard drive setup just install your anti-virus, imaging program, data back up and recovery, and other tools you would need to fix software or OS problems.
However these older versions of Emergency Repair Disks are not effective or
will help with Vista and newer Operating Systems. You need a newer version of
ERD and if you want more than the five tools provided by Microsoft. You would
need a custom ERD,
click here to see how to make one (I made my custom ERD then put it on
my SSD external drive, very nice).
Which ever way you go when you have completed your OS installation don't forget to make that partition active. Nothing like needing it and it will not boot! (in other words test the darn thing!) Been there, Done That, it is embarrassing...