What I need
I need the boot image file for Windows so I can create my own Windows 10 custom ISO file and/or burn it to a DVD and make it bootable.
For example, in WinISO there is a menu option called "Set Boot Image" where it expects a boot image file to be specified, with the file name extension bifx or bif, or img.
What I have tried
- Downloading the boot image from the web
At first, I thought I could easily download one of the millions of boot images from the web. But after two hours of searching the web, I have not found anything I could use. Well, I found only one site that had it and my anti-virus program warned me not to go to that site.
Why is the boot image so hard to find? Is it copyrighted material?
- Extracting the boot image from an ISO file
I then tried to extract the boot image from an existing ISO file using WinISO. However, WinISO can only extract it from a physical CD/DVD. What I have here is the Windows 10 ISO file (64 bit, version 1909) which is more than 5 GB (5,294,394 Kb) and cannot fit on a single layer DVD-5 (4.7 GB). Therefore, I cannot burn the ISO file to a DVD in order for WinISO to extract the boot image (unless I have a double layer blank DVD-9 (8.5 GB) disc). I guess the programmers of WinISO didn't expect people to extract boot image from existing ISO files.
Is there any place where I can download a boot image file (bifx, bif or img) or any way to extract the boot image from an existing ISO file?
Clarification
I am looking for a boot image FOR Windows, not the bootable image OF Windows.

etfsboot.comin case of Windows 10 and can be easily obtained by taking theWin10_1909_English_x64.isofile that you already have and mounting it in a virtual disc drive, either natively by double clicking on it if you're on Windows 10 or by using a third party software like Daemon Tools or Virtual CloneDrive to mount it. The file can be located in thebootfolder and it's only 4,096 bytes in size and MD5 is D4BEFEBF3CEF129AC087422B9E912788 (in case you decide to download it from the web). – Samir May 16 '21 at 23:12bbie.exe(Bart's Boot Image Extractor v1.0, (c) 2001, Bart Lagerweij) which used to be hosted on nu2.nu but the site no longer hosts any of the old utilities. However, you can still find this tool on various software archive sites like Softpedia. This was used before Windows 10 was invented, even before Windows 7. I just tested it and it producesimage1.bin(2 KB) andimage2.bin(2 KB) dumps where the first one matches against the first 2 KB ofetfsboot.com. So it may not be fully compatible with Windows 10. – Samir May 17 '21 at 08:31bbie.exeworks against either ISO images or physical CD/DVD ROM drives, so you could try it. I see here that it has a options for generatingbootrecord.binandbootcatalog.bin. Also, I don't know what version of WinISO you used, but at least in version 6.4.1.5976 you can go to "Bootable" menu, then "Import From", and then "CD/DVD/BD Image File". It will produce abifx("Multi-Boot Image File", hence the X) in the amount of 1480704 byte (roughly the same as a 1.44 MB floppy, i.e. including the first 4 KB you may need). – Samir May 17 '21 at 08:45Win10_1909_English_x64.isofile in a virtual disc drive and then use UltraISO to extract the boot image from the virtual drive. I just tested this and it made aCCCOMA_X64FRE_EN-US_DV9.bif(uses volume label of the ISO file) which is 100% bit match againstetfsboot.com(4 KB). – Samir May 17 '21 at 08:59