Convert Windows 8 from UEFI to BIOS

omniscence

[H]ard|Gawd
Joined
Jun 27, 2010
Messages
1,311
I tried several weeks to get my P8Z77 WS to boot per UEFI from a QLE2560 FC controller and an X540-T2 per iSCSI (both work with BIOS boot). It just does not work. It seems to be an incompatibility between the board's implementation and the UEFI option ROMs on the controllers.

In the mean time I installed Windows 8 in UEFI mode to an SSD with a lot of software and would like to convert the installation to BIOS mode and transfer it to my fileserver for remote boot. One can find guide for the usual conversion from BIOS to UEFI, but not vice versa. My approach would be to make a fresh Windows install in BIOS mode and just overwrite the system partion with matching partition size. Since all boot information ist contained on the boot partition or EFI partition as far as I know, I assume this would work. I'm curious if someone tried that and was succesful.
 

BBA

Supreme [H]ardness
Joined
Apr 25, 2003
Messages
5,382
To prepare the working windows, its easier: Make sure you make a good Ghost backup (or any other full disk backup software type). You can go into device manager under 'Computer' and update the device to "Standard Computer" you will have to select the device manually, unchecking the 'Select compatible devices' option. It will be easier if you have the windows 7 drivers from the system board files. Once the driver is loaded, it will prompt for reboot. Say no, shutdown the PC, move the drive over to the BIOS system controllers, start up windows, it will then autodetect drivers (such as ACPI device).

I can't say what that will do to activation though...
 

omniscence

[H]ard|Gawd
Joined
Jun 27, 2010
Messages
1,311
That is not only a driver problem. The main issue is that BIOS cannot read GPT drives and EFI boot partitions, while UEFI does not accept MBR drives and the legacy (realmode) booting scheme. All drivers already exist on the OS I'm trying to convert. My questions was more like: Is it enough to just convert the disk layout or is an UEFI install fundamentally different from a BIOS install?
 

BBA

Supreme [H]ardness
Joined
Apr 25, 2003
Messages
5,382
Ok...sorry man, reading more into it. Converting it from GPT to MBR will not make the existing install bootable to windows as you will have to recreate the partitions in the conversion process.

Maybe go with make a backup of your data and use the migration wizards to export/reimport settings after the drive is setup on the other controller? I see some utilities other than disk manager and diskpart to do the conversion with, but all seem to have the same issues as the ones built into windows.
 
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