Which exact Windows 7 ISO is required for Boot Camp v6.1.0 on macOS High Sierra? Mid 2010 MBP
Steps to Install Windows 7 without Using the Boot Camp Assistant

Although a Windows 7 can be installed without using the both the Boot Camp Assistant and a Windows 7 installation DVD, the using a the DVD greatly simplifies the procedure. Since you have a working optical drive, I the steps given below will include using this drive.


  Note: According to Apple, you need a Windows 7 DVD with Service Pack 1 (SP1) included.


Create the Flash Drive with the Windows Support Software


Use the Disk Utility to erase a 8 GB or larger flash drive. For name, use WSS. For format, use MS-DOS (FAT). For scheme, use Master Boot Record.
Download the "Windows Support Software" for you Mac from the website Install Windows 7 on your Mac using Boot Camp.
Copy the "Windows Support Software" to the flash drive.
Under Safari preferences, select Advance. Make sure Show Develop menu in menu bar is checked off. See image below.


From a window opened in Safari, go to the website https://sourceforge.net/projects/gptfdisk/. While at this website, select Develop-&gt;User Agent-&gt;Microsoft Edge from the menu bar, then click the Download button on the webpage.
From the downloaded files, copy gdisk64.exe to the root folder on the flash drive.
Either close the Safari window or select Develop-&gt;User Agent-&gt;Default from the menu bar.


Install Windows 7


  Note: If during the installation of Windows, the Mac restarts back to macOS, then open the "Startup Disk" pane of the "System Preferences" application and restart back to Windows. The installation of Windows will continue from where it left off.



Use the Disk Utility application to partition the internal drive.  Add a new partition named BOOTCAMP with the format MS-DOS (FAT).


  Note: after partitioning completes, you may have to quit and then open the Disk Utility application to see the correct results.

Insert the Windows 7 DVD in the optical drive. 
Insert the Windows Support Software flash drive in a USB port.
Restart the Mac and immediately hold down the option key. Release the key when the Startup Manager icons appears. Select the icon labeled Windows.
When the window below appears, select Custom (advanced).


The BOOTCAMP partition should be either 3 or 4. Remember the number, you will need this later.
Press the shift+F10 key combination to open a Command Prompt window.
Enter the command shown below. Remember the drive letter (name) for the  WSS volume.

wmic logicaldisk get name,volumename

Enter the command below to execute gdisk. If drive letter (name) for the WSS volume is not D:, then make the appropriate substitution.

D:\gdisk64 \\.\PhysicalDrive0

Change the type of partitioning to hybrid. If the BOOTCAMP partition is number 3, then enter the commands given below.

r
h
2 3
y
ff
n
07
y
n
w
y


Otherwise, if the BOOTCAMP partition is number 4, then enter the commands given below.


  Note: If macOS is using encryption, the substitute ac for af below.


r
h
2 3 4
y
af
n
ab
n
07
y
w
y

Enter the exit command to close the Command Prompt window.
Click on the Refresh button.
Select the BOOTCAMP partition. Before clicking the Next button, you will have to format the partition by first clicking on Drive options (advanced), then clicking on the Format button.
After finishing installing Windows 7, execute the setup application on the Windows Support Software flash drive.