Prearrangements and Pretest

Preparation of an USB storage device for being booted

An USB storage device has to be prepared before being usable as a bootable host for an installation of Windows.

Please note that the BIOS of your computer and/or the firmware of the USB device may imply some special needs to or put some restrictions on the way both your system and your USB device have to be set up to allow Windows to be booted from USB.

Once you managed to effectively boot up from USB you may try your luck with less conservative settings than the ones recommended here.

1. Wipe the disk clean

To be on the save side it may be worth the trouble to accomplish a full erase of the USB storage device. Zeroing out any residual data in areas that are crucial for the boot process like the MBR, partition table and partition boot sectors may help to prevent unforeseen incompatibilities and side effects. In fact it would be sufficient to simply write nulls to the relevant places but for most users a full wipe is accomplished more easily even if it may admittedly take its time to complete.

Though this step is not mandatory it should be especially considered in case the boot process does not get through to the Windows boot menu.

2. Partitioning

Create only one single primary partition on the USB disk and mark it as the active boot partition on that device. You may use the built-in tool of Windows to perform this task (Context menu of 'My Computer'-> 'Manage' -> 'Disk Management'). In the same go with the partitioning information there will be usually written the executable loader code into the MBR.

For a start you should keep the size of the partition quite small (less than 4GB) as your configuration (BIOS etc.) may implicitly put some restriction on its size. Apart from that distinct utilities used for partitioning may provide you with varying executable code in the MBR. In some cases this may make the difference between success and failure! So it could be worth a try to give various tools or even operating systems a chance.

3. Formatting

Format the partition with a filesystem that as well supports loading of NTLDR as it is being supported by NTLDR for loading the Windows boot core. Actually there are three filesystems that match these criteria for the standard bootloader ntldr:


In general FAT seems to be the one that faces the least risk of incompatibilities, followed by FAT32, while NTFS is rated a bit picky in certain settings.

4. Pretest

At this point you may execute a simple pretest that will give you an indication of your chances to boot Windows from USB with the present configuration. Therefor three files have to be copied from the root directory of an installation of the kind of Windows you want to use on USB to the root of the freshly initialized USB partition:


The first two of them are usually marked as 'hidden' so that you will probably have to adjust some option to make them available in the Windows file explorer (not the internet explorer!). Furthermore you have to make sure that boot.ini contains at least two valid entries (lines) in the '[operating systems]' section.

Here is an example for the content of a boot.ini that may be used for this kind of pretest:

[boot loader]
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="If these lines are displayed on your screen... :-)"
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="...chances are good to be able to run Windows from USB!"

Then try to boot from the USB storage device.

Of course you will not be able to perform a full start of Windows this way but if the boot menu is being displayed it is very likely that the boot of a full Windows will succeed in this configuration (BIOS/MBR/hardware/partitioning/filesystem/os version/loader).

Created by admin. Last Modification: Friday 17 of January, 2014 13:42:46 CET by admin.