Q: Failed Windows 7 install, 2008 iMac running 10.11.4: no bootable disk found

I am having great difficulty installing Windows 7 on a 2008 iMac running the latest OS X El Capitan, 10.11.4. The exact procedure followed is based on this Apple Support document, with a couple of modifications:

https://support.apple.com/en-us/HT205016

The first modification is to the Boot Camp Info.plist, three changes to account for this being an older Mac:

(1) Adding a string for the Mac’s ROM version: <string>IM81.00C1.B00</string>

(2) Changing <key>PreUSBBootSupportedModels</key> to <key>USBBootSupportedModels</key>, i.e. delete ‘Pre’

(3) Adding the string that identifies this Mac: <string>iMac8,1</string>

Running Boot Camp Assistant again, I can then tick the three boxes available in Select Tasks, as per the screen shot in the article cited above.

The WININSTALL flash drive is then created, from a legitimate Windows 7 32-bit ISO file.

The second modification relates to points 8–11 of the article cited above, which mentioned that the following files/folders need to be added the flash drive:

$WinPEDriver$ (folder)

AutoUnattend.xml

BootCamp (folder)

Supposedly the correct support software for this 2008 iMac is the following, 4.0.4033 …

https://support.apple.com/kb/DL1630?locale=en_US

… but after downloading this and unzipping it, I am not finding the required files/folders.

So I dig around on this other page, looking for other Boot Camp downloads where these files/folders might be present:

https://support.apple.com/downloads/bootcamp

Curiously, some of these downloads do contain the three files/folders, and some do not. So I download the very latest Boot Camp Support Software, 5.1.5722:

https://support.apple.com/kb/DL1836?viewlocale=en_US&locale=en_US

I find the three files in this download and drag them over to the flash drive. The entire list of files on the WININSTALL drive is now as follows:

I then proceed again with Boot Camp Assistant, i.e. the third tick box on the Select Tasks screen, the installation process only.

The install stops when the Mac re-initiates itself. The following message appears on-screen against a black background:

“No bootable device -- insert boot disk and press any key”

I have tried this procedure multiple times and with different flash drives, with the same result.

Re-starting the Mac with the ‘alt’ key shows that the Mac’s normal hard disk is available for selection, but no Windows disk is present. So has the partition even been made?

I am stumped. Any advice would be much appreciated, thanks.