Making a Windows 7 Installation USB Stick

Question

This is a discussion of making a bootable Windows 7 Installation USB-stick Media. It might apply to making other USB connected "Disks" like Smartcards bootable too.
I recently had to do this (a Laptop with no build-in DVD drive and no USB DVD drive around). And it turned out to be surprisingly simple, using nothing but build in Windows tools from the Disk. I only found
this german langauge guide and nothing in english (but I might just have searched after the wrong terms, google has been wierd regarding langauge lately), so I thought I write it up (along with some problems I ran into).
Making a USB-Stick into a bootable Windows 7 (and propably Vista) Media is a 3 step process:
1. Create a Active, Primary, FAT32 Partition of 4+ GB on the stick
2. use bootsect.exe from Windows Disk to create the MBR and Partition Boot Record for that Partition
3. Copy all files from the Disk to said Partition
4. Test if it boots
Detail analysis:
Step 1 is so simple I doubt it needs explanations. Create enough free space on the USB disk (at worst delete all previous Partitions). Make a Priamry Partition of 4+ GiB. Mark it as Active. Format it in FAT32. The Guide used Diskpart,
but this step can be done with any Partition Tool under any Windows, Linux, UNIX or DOS.
While the choice of FAT32 seems a bit outdated, theye propably did not gave the relevant bootlaoder the ability to read NTFS. Or maybe they just though FAT32 is enough for a media that is mostly read. I have not tried what happens if I format it in NTFS, but
it might be possible.
Step 2 was the only tricky part. You need the programm "boot\bootsect.exe" from the Installation Media. It also must be run on a non-UEFI booted OS (otherwise it cancels out).
I had a Windows 8 on a new Laptop so I had a UEFI booted system. Luckily I also had a VMWare Windows 7 lying around. I just assigned the Windows 7 ISO image to the Windows 7 VM, then connected the USB drive to the host.
Once you have the USB stick in a a proper Windows mount the Parttion you created under 1 under any driveletter (should happen automatically under Windows), and open a console as Administrator (asumes DVD is drivletter is D: and the USB stick's partition
ins Driveletter E:):
//Go into the boot directory on the Install DVD
D:
cd boot
//You should see a command promt like "D:\BOOT>"
//Run bootsect.exe
bootsect.exe /nt60 d:
Step 3 is to either copy the contents of the DVD media (copy and paste) or the Image (Mount into Virtual DVD Drive and copy/paste, unpack ISO images contents) into the partition.
How does this compare to other Distribution ways?
To DVD:
There is no need for a DVD drive. Even if a bootable USB-DVD drive is avalible, the Stick or Card will only need only USB port (most USB drives need 2 Ports due the 1 Ampere energy need of the drives).
Flash Media has no seek times and much better throughput (the old weakpoint of any Disk and DVD/CD in particular)
A FAT32 partition is inherently writeable. So modifications to the "Installation media" like Implementing Service Packs and other Windwos Updates, Modifying ei.cfg/preactivation/setup answer files, implementing special Disk/RAID drivers into the Windows
PE or adding stuff that should be installed with Windows is easy (and do not requrie reburning a 4 GiB Image file).
Since it only needs a 4 GiB partition, on a big USB stick there would still be place for other Data Partitions
Since it relies on old techniques (Generic Bootloader + Active Primary Partition + partition boot loader), multiple Installation media on a big enough stick might be feasible (with a more advanced bootloader like GRUB). Have to test that part.
However, the cost/media is a lot higher then a DVD. So if you need multiple Medias it will propably be cheaper to use the old DVD approach.
Due to the needs of bootsec.exe, first creating the media can be more difficulty then just burning an image. But once it is bootable this programm is no longer needed.
To PXE/network Distrubution:
If you have the nessesary setup already (DHCP/PXE Server, powerfull network), the USB stick is likely inferior. The USB stick should beat a 100 MBIT Network easily, but will propably be beaten by a 1 GBIT Network. Network isntallation uses existing infrastructure
(that you need for other reasons anyway) so the cost per media is even lower then the DVD.
The PXE way also has even better modifyability - sending out different answer files or even automatically booting different images based on the Compuers MAC adress are tried techniques.
If you lack the nessesary setup, the USB stick is a lot easier to implement and a lot easier to transport.
Advanced things:
Need to check if the partition could be formated as NTFS. I prefer a Journalling Filesystem for my USB-sticks.
Need to check if using a advanced boot manager techniques (like Grub or modifciations to the BCD of the Windows PE) allows me to put multiple install media on one Stick (with one primary partition per "media"). Especially combining the x32/x86 and
x64 Windows Installation Media would be worthwhile. As would be inlcuding a Window 8 or Vista installation media.
Current Step 3 and 2 can propably be switched. I see no reason bootsect could not run from the USB stick as it runs from the DVD (it only accesses the MBR and
VBR of the Disk, areas not in use by Windows)
Steps 1 through 3 might be possible from the Windows PE environment. If so, only a computer with legacy BIOS boot would be nessesary (no actuall installation).
Windows 7 can be installed on a (U)EFI system, but I have not checked if I can use the boot from teh stick on such a Computer. Latest for Windows 8 Media UEFI compatibilty is nessesary.
Let's talk about MVVM: http://social.msdn.microsoft.com/Forums/en-US/wpf/thread/b1a8bf14-4acd-4d77-9df8-bdb95b02dbe2 Please mark post as helpfull and answers respectively.

Answer 1

Advanced things:
Need to check if the partition could be formated as NTFS. I prefer a Journalling Filesystem for my USB-sticks.
Windows 7 can be installed on a (U)EFI system, but I have not checked if I can use the boot from teh stick on such a Computer. Latest for Windows 8 Media UEFI compatibilty is nessesary.
I converted the stick to NTFS using the convert.exe and it continued booting. So chances are high they only choose FAT32 in the example because no feature of NTFS was per nessesary in a "almost only reading" scenario like installation media.
The second part depends on the BIOS. I have a more advanced one where I can choose legacy boot options (like USB stick) in the boot option menu even when the default setting is UEFI, as long as I don't need Secure boot (wich I do not).
Another question arose: Windows 7 has the Kernel/BCD level ability to boot from .VHD Files. The only thing preventing version below corporate from using this feature is a license check that is run just before the login (so way after the booting has been
completed).
Starting with 3.0 Windows PE is based on the kernel of Windows 7. So the instlaltion system might have the ability to boot from .VHD too and might have no such check in place. If so, I could put both versions of the Windows 7 installer into .VHD, reducing the
need to have physical primary partitions for those.
Windows bootprocess vs. Linux boot process under BIOS:
The BIOS goes over all the boot media. If it finds one with a MBR, that one is executed and the BIOS part of the boot process is officially over.
 -> Under Windows the MBR contains the "generic boot loader". A simple piece of code as old as BIOS (25 Years) that looks for the primary partition with "Active" Flag on "it's" disk. If it finds one, the Partition Boot Record of that parition is executed.
The MBR has done it's part
    -> NTLDR (NT too 2000), this one reads the boot.ini file and gives/executeds apropirate options
    -> BOOTMGR (Vista, 7), this one reads the BCD files
      -> Since Windows 7 BOOTMGR can also chainload the Partition Boot Record that is inside a .VHD File
    -> Wicher was used in Windows 3.X/95/98/ME
Higher versions can chainload lower versions, but must be designed for this and (re)installed in the proper "order".
The sometimes odd behavior that Windows 7 tries to keep 100 MiB in a seperate primary partition is there to have proper places for later additions to the BOOTMGR settings. Specifically it allows multiple BOOTMGR OS to use/edit the same BOOTMGR instace without
running into problems with "whose partition is active?" (since it is always the System Reserved one). It's not disimilar to having an extra /boot partition in Linux or how a GRUB's stage 2 works.
-> Under a typical Grub Legacy the MBR contains the Stage 1. It directly reads the Stage 2 from the proper partition/file system with a hardcoded path, but due to size limit of the MBR cannot do more. In some cases it starts a stage 1.5 wich has more
space to do work (63 sectors between MBR and first partition), but I never used this Setup
    -> Stage 2 loads the Grub Configuration from the disk. From here it depends on what OS you want to boot.
        -> For Linux or Unix the kernel is started directly.
        -> Any Windows OS up to 7 can be booted using the chainloader command. For the OS this is identical to having the partition choosen by the Generic Bootloader.
While it can be chainloaded by the Generic Bootloader from the active primary partition, GRUB and thus Linux has no
requirement for any Primary Partitions. Stage 1 is designed to directly access the specific File System containng the Stage 2. In fact it does not even need to reside on the same disk (as the Generic Bootloader has to).
If one does not need the Active Flag to control the Generic Bootloader (because a proper Stage 1 is installed in MBR) it is adviseable to mark wichever Windows Partition is chainloaded as active (up to Vista at least I had very odd behavior if the Windows boot
partition was not marked active, down to randomly shredded Partition boot managers).
After running a Windows Setup usually the Stage 1 has to be restored, as Windwos Setup will always write it's Generic Bootloader in the MBR. In order to get "rid" of a Grub all one has to do is overwrite the MBR with the Generic Bootloader and set the active
flag properly.
Let's talk about MVVM: http://social.msdn.microsoft.com/Forums/en-US/wpf/thread/b1a8bf14-4acd-4d77-9df8-bdb95b02dbe2 Please mark post as helpfull and answers respectively.