quote:

Originally posted by 4MUL8R:
Created a USB boot OS X stick. Was able to select it as a bootable disk by holding down option key. Machine did the same thing again...ding tone, apple logo, progress bar to 2/3rds, and then grey screen forever.

Have you tried booting into single user mode (hold down Command-S while booting). If so, you can at the very least run fsck and see if it fixes any file system issues. If it will boot that far, read up on it if you're not familiar with single user mode and fsck. macOS runs this during a regular boot, but in SUM you can force some overrides to fix problems. SUM runs at a very early time in the boot process.