I started with a 64Gb Verbatim SDXC which always worked okay (as a non-booted disk) in my Sony VAIO. Etcher 1.4.4 indicated success at flashing a 1.76Gb disk ISO (Linux Mint 19 xcfe install/live DVD) onto said SD card.
Then I went into the VIAO BIOS and enabled ‘external drive’ as a boot device. Reboot yielded black screen with top left blinking underline. I waited a few minutes before re-entering BIOS & restoring to HDD (Windows) boot.
Now, the 64Gb SDXC shows as 2.25Mb. I can re-format it, device manager says ‘device is working okay’. I tried putting it into my Camera, but it just says ‘SD Card Error’ or some such.
Funny(?) though, I ran Etcher again, and when I select the drive it reports it as 62.56Gb. I re-etched the same ISO file, Etcher ran again with no errors, but Windows 7 64 bit still says a capacity of 2.25Mb.
Is there any way to recover the full capacity of the SDXC card? Probably I should give up trying to boot UEFI on this PC; I was not sure if it would work but I figured it couldn’t break anything. Obviously I was wrong and lucky I didn’t brick the whole damned PC.
In the old says, there were DOS diskettes one could boot which would then boot from a CD if the BIOS could not do so directly. Is there perhaps something similar to that which can boot UEFI devices from within a running Windows sytem? (I suspect the VAIO bios more than Etcher of corrupting the SD card.)