Chosen Solution
I’m trying to install El Capitan onto a 2008 iMac. I’m installing it onto an SSD that has been installed in place of the internal optical drive using an iFixit enclosure. I keep getting an error saying, “OS X could not be installed on your computer An error occurred while updating system extension information. Quit the installer to restart your computer and try again.” This is the second drive (from Crucial) that has given me this error. I had another drive in that internal enclosure that worked just fine until it SMART failed. The drive passes all TechTool Pro checks. The problem doesn’t seem to be the drive. OS X installs to the internal HDD just fine. What’s going on? imac_c2d_osx_install_fail_2017 Here’s the Installer Log.
I’m wondering if the SSD you got is able to run in this system. Keep in mind Crucial MX300 SSD only states support for SATA III (6.0 Gb/s). Review the system specs I posted in your Q) I think you’ll need to try a different SSD here. Some earlier Crucial SSD models did have auto sense allowing them to work in the older SATA II (3.0 Gb/s) systems. I don’t think the Crucial still sells it. I would give Samsung a try: Samsung 850 EVO Here you can see Samsung supports all three SATA data rates “SATA 6Gb/s (compatible with SATA 3Gb/s and SATA 1.5Gb/s)” unlike the Crucial MX300 SSD.
