Bios only sees one bootable drive but boots to the other

Hi Folks,

I built a system outside the case, no problems. Made it a dual boot with windows pro all drivers up to date. Installed it in the case and now the bios only sees one of the m1 drives as bootable but doesn't boot to it and instead after a while on a black screen it boots to the other drive. Not sure what happened but before I wipe both M2s and start over I was wondering if anyone had any ideas? Its a new 590 Tuff asus system with a 11700k i7 and 32 gb ram. 2 M2 drives one 250 and one 1 tb. Running on on board video for now.

When it boots into the other drive it does see both drives and bios also sees both drives but only one as bootable and it isn't the one its booting into.

Ideas welcome!

Windows build 19042.1645

ok this just got weirder. I went back to it to grab a disk manager screenshot and if I power the computer off and turn it back on both windows versions come up but if I reboot without turning it off, it disappears.

Its not the end of the world for me to install windows again even if its on both but what could be the cause for this?

Samuria said:

It boot from disk 0 and the system is on disk 1 there is no uefi parition on disk 1

There's actually 2 OSs one on each drive. When its powered off and turned back on, both show up but if it remains on and rebooted, it only boots off disk 1 and the boot menu doesn't come up. I can boot into each if its from a powered down state

well strangely enough when I added a vid card and stopped running off the on board video the problem went away. thanks to everyone for their suggestions