The Windows 7 ISO does not contain drivers for USB 3.0 controllers or drivers for some of the more recent USB 2.0 controllers.
If you make a bootable USB drive containing Windows 7, you may find that you get a 'required CD\DVD driver is missing' error message because it cannot find the USB drive once Windows WinPE has loaded.
One alternative to installing Windows 7, would be to run WinNTSetup.exe from a Windows 10 WinPE USB drive and then load and install the Windows 7 ISO using WinNTSetup.
Alternatively, it is possible to add Windows 7 USB 3.0 drivers to the Win7 installer files, however you might like to try this way instead.
It does not add USB 3.0 drivers to the installed Windows 7 OS, so you may need Network and/or Windows 7 USB drivers on a CD\DVD once you have installed Windows 7.
8GB+ USB Flash drive (USB 3.x or USB 2.0)
Windows 7 ISO
Windows 10 ISO (latest version you can find from Microsoft - do not use a dual 32-bit+64-bit version)
IMPORTANT: The two ISOs (7 & 10) should have same CPU type (i.e. Win7 32-bit + Win10 32-bit, or Win7 64-bit + Win10 64-bit)
We will make a bootable Win7 USB drive, but then add the Windows 10 boot.wim file and Setup.exe files.
1. Run RMPrepUSB - select BOOTMGR option + NTFS + Boot as HDD
Add Windows 7 ISO in Copy Files box
Click Prepare to format USB drive
This should make a bootable, Windows 7 installer USB drive - check it boots OK (at least to the start of Setup).
2. Copy \Sources\Setup.exe and \Sources\boot.wim from a Windows 10 ISO (use 7Zip or Windows 10 Explorer) ==> USB:\Sources\ folder.
Overwrite the files if prompted.
3. Delete the USB:\Sources\EI.cfg file so that you will be given all choices from the Windows 7 install.wim file (optional)
4. Now you should be able to boot from the USB drive to Windows 10 Setup, but install Windows 7. Use 'I don't have a Product Key' to skip that screen.
If your internal hard disk previously contained a GPT partitioned disk, you will have to wipe the disk as follows:
1. In Windows Setup, pressSHIFT+F10
2. At the command shell, typeDISKPART
3. Find the internal hard disk that you want to install Windows 7 onto by typing LIST DISK
4.SELECT DISK n (where n is the disk number)
You will not be able to access the USB 3 ports when running Windows 7 until you install the correct Windows 7 USB 3.0 drivers.
These drivers can be obtained from the internet (if you have suitable network drivers installed!) or from the manufacturers driver CD\DVD disk (if you have a SATA DVD\CD drive fitted).
Tip: Boot from the USB drive once again after installation, and use the SHIFT+F10 feature to copy the correct USB 3.0 and Network (Ethernet + WiFI) drivers from the USB drive to the hard disk once Windows 7 has been installed, then boot to Windows 7 to install them from the hard disk.
You can use the command line to copy the files, or run Notepad from the command line and then use the NotePad - File Open dialog box to copy files by using right-click operations.
To add this to Easy2Boot, run MakePartImage.cmd (from the MPI Tool Kit) and choose the USB drive as the source path to make a .imgPTN file.
To support UEFI-booting, you will need to also add \EFI\boot\bootx64.efi from the Win10 ISO (untested).
Note: If you convert the USB drive to an ISO, and try to use the ISO with Easy2Boot it probably won't work!