> I get the error Message that "installboot: /mnt/usr/mdec/biosboot extends > Beyond sector 268435455. OpenBSD might not boot." I'm dual booting with > Windows using Windows' boot loader first.
You've created an OpenBSD MBR partition too far up your disk. It won't work in legacy mode. The BIOS won't be able to read it. You can try EFI mode instead.
