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Question New MOBO doesn't find old disk with windows

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floky99

Joined
Mar 22, 2021
Messages
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Hello,
I have just bought a new mobo for PC which is ASUS PRIME B460M-A R2.0.
Mobo recognizes my old disk: Samsung SSD 850 EVO but doesn't find it as bootable media...
I've googled a bit and I have seen that I should maybe enable CSM mode but it's greyed out and disabled on this specific bios not sure why...
Then I've also read that disabling fast boot and secure boot could enable CSM mode to not be greyed out but it didn't help, it's still greyed out and also disk is not visible as bootable media...
When I plug this disk back to my old mobo everything works. Does anyone know what seems to be the problem?

Thank you in advance!
 
what you did should fix that, Is the disk visible at all in the UEFI? But even without disk you should be able disable secure boot and enable CSM, maybe reset UEFI(BIOS) and try again
you can also take a pic with with UEFI page with secure boot and CSM settings and post it here
 
Was your original motherboard BIOS set to SATA or ACHI? It makes a difference.

If your original BIOS is set to ACHI and the new motherboard defaults to SATA it will not boot to the disk. It will give that error.

Also make sure that your first boot device is set to the 850 EVO Windows boot. Sometimes it will default to something else.
 
Shihabyooo said:
Is reinstalling the OS not an option?

You could try a startup repair using a Windows installation disk/thumbdrive or good ol', one-click, boot repair disk. Might work if this was a bootloader incompatibility issue between the two mobos. Note that this *could* potentially break boot-ability with the old motherboard.
Click to expand...
I really don't want to reinstall the os since I have a lot of data on that disk that I don't want to lose...

stinger608 said:
Was your original motherboard BIOS set to SATA or ACHI? It makes a difference.

If your original BIOS is set to ACHI and the new motherboard defaults to SATA it will not boot to the disk. It will give that error.

Also make sure that your first boot device is set to the 850 EVO Windows boot. Sometimes it will default to something else.
Click to expand...
I'm not sure which mode was my og motherboard...
In the boot manager I don't see any devices like I mentioned, but I do see my disk on devices in BIOS
 
Your old disk must have been formatted as MBR and not GPT, and installed in CSM mode


You can either format the drive to GPT and reinstall windows, or find out how to enable CSM on your motherboard
 
what guys mentioned here is valid if you are already able to choose your boot device but at this point for legacy boot are not relevant - you should be able to choose even empty disk as boot drive for legacy mode (ofc it will not boot, but will look for boot partition on that drive at least)
as I said, taking pics of relevant UEFI/BIOS pages and posting them here would help to troubleshoot the issue
 
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