The official way to get Windows booting and running from a USB connected hard drive is by way of something called Windows-to-go which is only available in and for the Enterprise edition of Windows-8. There is a way however to get any version of Win-8 bootable from a USB drive, and it can mostly be done by point and click in any version of Win-7 or 8, (for other OSes see Tech-Bench below). Windows-to-go can also of course make a bootable USB thumb drive, which we will be able to do after we have made our USB booting hard drive. Running Windows 8/8.1 from a USB/SD Flash Stick or Card.
You do have to possess a copy of Windows-8 (see box below) and be capable of installing a Windows operating system. The intended hard drive would ideally be wiped blank and then repartitioned and configured as we require, which we can do entirely from any version of Win-7 or 8 using the Disk Management utility. It will not matter how the target drive is connected for this, be that by SATA or USB, as it just needs to be seen by Windows. When we come to install the Win-8 operating system however we will need the drive connected by SATA, either internally inside a machine, or by way of an eSATA external case, dock or leads.
We don't have to build our drive on the machine we intend to use it on, as it will be capable of adapting to and booting up on most common and reasonably up-to-date hardware. Performance will be limited by the speed of the USB connection, so for anything more than just the testing of Windows-8 or for occasional and limited use, a USB 3 connection would be desirable. An SSD hard drive is unlikely to provide much benefit as it won't improve on the limit of the read/write speeds of the USB connection. The size of the drive can be anything that is normally supported by the software and hardware of the machine it is plugged into, but a small drive will suffice for just a functioning Win8 install. If we want to go on and make a USB/SD flash device then we will have to keep things small.
Our first screenshot here in fig:1 is of the Windows Disk Management utility that we have open and running from inside the Windows-7 operating system that our machine is currently booted into.
Our new Virtual Hard Drive will immediately show in Disk Management as if it was a real drive. In our example it is listed as Disk 2 and it is identified as a virtual drive by the small blue colored drive icon. You can check everything went correctly to plan by looking on the target drive (G: in our example) in Windows Explorer for the presence of a single .vhd file with the name you gave it and a file size of 16gigs.
If you have no plans to later use this project to make a Win8 bootable USB thumb drive then the partition on the target drive and also the virtual hard drive can be made much larger if you think you may want extra space in Windows. We suggest you keep at least a 4 gig difference between the size of the partition on the physical drive and the size of the VDH so that Windows on the virtual drive can locate its swap file on the physical drive, which it will have a mind to automatically configure if possible.
Any unallocated space left on the physical drive can be turned into a data partition, or if you are adventurous used to make the drive dual or multi-boot with additional operating systems, or you can later just simply expand the physical partition to fill all the available space.
Apart from one small addition that we have to make during the install setup, the process of installing Windows is no different than normal. We need our hard drive connected through a standard SATA channel, then we boot the computer from the install media, either DVD or USB flash device, and point the install to the drive and partition we want it to use.
Ideally we want our drive to be the only one connected during the install so that we can be absolutely sure all of the Windows boot components go to the Active partition on that drive, only then will it be bootable from USB. If you plan to try this while there is another hard drive connected then be aware that simply changing the bios boot order to place our target drive first in the boot list may not over-ride how the Windows install environment will see the drives by their SATA channel numbers. If the target drive is not correctly seen as the boot drive then the Windows boot files could go to the wrong drive, which will not only result in our target drive not being independently bootable, but will see the other drive altered for dual boot by having its boot files reconfigured or replaced.
Start by typing:-
and pressing Enter.
Wait a few seconds till a few more lines of text appear and the Diskpart utility is loaded.
Next we have to type a command to get our VHD file seen. Ours is called win81v but you will of course use the name you gave to yours.
select vdisk file=c:\win81v.vhd
and press Enter.
Wait just a few seconds till you see the success message, then type:-
and hit Enter,
The following fig:15 shows what the entire exchange should look like.
The 20gig partition called New Volume that we created as the first partition on our physical target hard drive should be first in the list and show as Partition 1: on Drive 0 and additionally be marked under Type as System. If any of this is not correct then you should back out of the install and try again. If you are attempting all this while there is another hard drive connected and it is that drive that is being seen as Drive 0, then it will be the System partition on that drive that will be designated as the C: drive, hence our progress will he halted at the command box when our command select vdisk file=c:\win81v.vhd fails because our target partition has been given a different drive letter.
Once you successfully have Windows up and running you can start using or tweaking it or you can take it off the SATA connection and immediately use it from USB on most PCs. Your build machine should be totally unchanged and unaffected and if you use a computers' built in Bios Boot Menu to select and boot USB drives then you can have dualboot without having to make any fundamental or permanent changes to a machine. You can have Linux on another USB hard drive or flash stick/card and so have multiboot capabilities. If you progress to configuring a single drive for multibooting then you can have various operating systems on one USB hard drive.