Since macOS Tiger, Leopard and Snow Leopard was available on CD only, you would have received the original macOS with your MacBook when purchased, which can be used to reinstall after erasing. Obtaining service for your Apple product after an expired warranty A 2007 MacBook is obsolete, so we're not finding the Tech Specs to see which macOS it came with. Then you may be able to only install the macOS version which came with your Mac.

When downgrading the macOS for an older machine, you'll need to erase first.

Thanks for using Apple Support Communities! We see you have a question about installing an older version of macOS to your MacBook 2007, and we'd like to help.