Trying to install new GPU

[chrcoluk]

check the ahci setting in bios and toggle it to see if windows boots.

You cannot flip ahci on/off on a whim without issues once windows is installed, and the bios upgrade may have switched it.

 

[george1976]

I have an old Z68xp ud3 and when I flashed the bios it would reset to ide and windows wouldn't find a drive to boot, in my case just changing the option to ahci worked.