Uninstall High Sierra

For a MacBook that old (Powerbooks dropped off the market somewhere around 2005), you will likely need to use the Snow Leopard DVD that shipped with the Mac.

You can try Internet Recovery, but it only works on 2012 and later, or 2010, 2011 models that you installed the firmware update to use Internet Recovery.

On restart, hold down cmd-option-shift-R. If your Mac supports it, you will see a spinning Globe instead of an Apple. It will boot from Apple's servers and will install the OS that shipped on that Mac. However, it had Snow Leopard at best, so I think it will install Lion.

You will need to erase the drive and reinstall OS X. There is no way to go backwards without erasing the drive. Did you make a backup before upgrading? If so, just boot into Recovery and Restore from a Time Machine backup.

Here are Apple's instructions: macOS Sierra: Revert to a previous macOS version

Nachoson wrote:

I'm getting the spinning globe, but only gives me option for High Sierra even when using those commands. Everything is backed up, hard drive is erased. Disk drive is not working since High Sierra update. Kind of stuck

Did you erase the disk drive device? If you selected Macintosh HD and erased that, that is not the disk itself. That is just one of a few partitions on the drive. If it detects a Recovery partition on the drive, it will install that OS.

I don't know if the IR Disk Utility looks like the HS one, but if it does, you need to select Show Devices from the Sidebar popup menu above the disk list. Then select the actual device and erase it. Might need to use the Partition tab: 1-partition, Mac OS Extended (Journaled).

However, since that Mac shipped with a DVD OS, I don't know what IR will try to install as the "Shipping" OS. I thought it would be Lion.