Installing MAC OSX El Captain on iMAC 2007

If you can

• Reinstall the original OS from the optical recovery discs
• Download the El Capitan installer .DMG to a USB flash drive, using a modern Mac or PC
• Transfer the .DMG to the old Mac using the USB flash drive

then you might be able to open (mount) the .DMG (disk image) on the old Mac, and run the El Capitan installer application inside.

A 2007 iMac would have come out before the introduction of Internet Recovery, and would have shipped with a set of optical discs to use in reinstalling the original version of Mac OS X if something bad happened.

If you could use Internet Recovery at all, it would only be because of having once upgraded to Lion or later.

Hi,

I just wonder if Recovery over the internet doesn't work.

Use macOS Recovery on an Intel-based Mac – Apple Support (AU)

Fabio-iMAC wrote:

Unfortunately I didn't find yet the optical disk but I did not simply put the DMG into the USB. I have used the TransMAC windows application to create a USB bootable drive. As you can see from the picture below I'm able to see the USB drive but I'm not able to boot from external drive in order to start the OSX installation. I even tried to restore the USB image to the internal disk without any success.

https://discussions.apple.com/content/attachment/5ff310ae-ab1d-472c-83c6-765ced3cde55

Well, then, you were doing something completely different from what I suggested.

You didn't find the restore discs that came with the computer. You didn't install an operating system. You didn't use the USB flash drive merely as a means to get an intact .DMG file to the old computer. You didn't use the old computer to mount the disk image and run the installer as a normal Mac application.

What you did had so little in common with what I suggested that I don't know why you told me "I did exactly what you said."

Fabio-iMAC wrote:

Not, I used the “restore image” function of the disk utility to put the usb image into the ssd. I thought that because the internal disk is bootable may be this would help but it didn’t work

The El Capitan .DMG image wouldn't be for a bootable volume. Just for a data volume containing an application which installs El Capitan.

If you had a Mac running the latest version of El Capitan, or something later, you could use that .DMG to create a bootable installer. But you don't have that … if you did, you wouldn't need a bootable installer.

How to download and install macOS - Apple Support

Create a bootable installer for macOS - Apple Support

Fabio-iMAC wrote:

• I did exactly what you said

Download the El Capitan installer .DMG to a USB flash drive, using a modern PC

• Transfer the .DMG to the old Mac using the USB flash drive

But as I said the Mac doesn't recognize the USB drive

Putting the .DMG file into the USB flash drive will not turn the USB flash drive into a bootable installer.

You must have some version of Mac OS X / macOS running on the old Mac in order to be able to use the file. Did you carry out the first step of finding the recovery discs and using them to install an operating system so that the old Mac would be able to use the old operating system to open the .DMG file and run the Mac application inside?

It looks like you have only put an El Capitan Installer on the Internal Crucial SSD.

Select the Crucial CT6...... and post a new image of the Disk Utility panel.

You will need to re-format and install OS X on the Crucial SSD.