For some very old system that doesn’t support hardware USB CD-ROM (ISO) emulators (or it only has USB 1.1 ports which is begrudgingly slow), there’s a way to put your installer in a HDD/SSD (IDE/SATA) and boot the installer image on them. Turns out it’s quite easy. All you need to do is copy the set of entire Windows installation files in an MBR drive with partition set active, then write the boot sector to it!

1. Make sure your HDD is in MBR, not GPT
2. Make a partition that’s bootable (can be NTFS) by marking it as Active (Active partition only make sense with MBR. That’s why you should make your disk MBR)
3. Copy all the files from Windows CD image to the drive
4. Run the following code the build the boot sector for the drive. One interesting twist is that you must run this command from the drive letter you want to rebuild the boot sector (or it’ll refuse to run) yet you have to specify what drive letter to rebuild the boot sector! Let’s call the drive P:\

P:\:> bootsect /nt60 P:\

The /nt60 is the modern boot manager for Windows 7 and above. /nt52 is Windows XP and old NT style (NTLDR) boot manager. Miss the old days when I was using winnt /b!