error no bootable device on mac book pro a1278 windows erased my macos saying disk was not usable

I installed windows on a external hard drive and booted on it when I booted on windows it erased the internal hard drive of my mac book by a prompt now no option key or other short cut is Woking .every time I start it it shows no bootable device install boot disk and press any key so I plucked out the internal hard drive and installed windows on it and I work ked that way then I wanted to install drivers so I downloaded mac os and made bootabLe pendrive I some how booted into it and then I found it was useless so I selected windows as startup disk by clicking on apple logo then ever science what ever I do only this error message

Posted on Mar 11, 2020 9:43 AM

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Mar 11, 2020 9:51 AM in response to Mecprox

If you ran any Windows-native software that makes ANY changes to the partition Map, it does not respect the MacOS partition structure and writes over it. Your MacOS Volume becomes unavailable. Windows does not acknowledge that there are other OS in the world, and that Windows might be a "guest" OS.

Some have said that Disk Warrior can recover form this, but that is not guaranteed.

In general, you will need to re-write the partition Map, which likely means ERASE the drive completely, by its immutable device-name, and start over.

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error no bootable device on mac book pro a1278 windows erased my macos saying disk was not usable