Windows self-converted from UEFI to legacy, and from GPT to MBR... and will no longer boot without recovery disc

[Guy Marshall]

Installing F4 from F3 worked fine, but after installing BIOS F5a on a Gigabyte Aorus Master sTRX40, my Windows installation would not boot. I thought the BIOS wasn't seeing the drive etc etc so I booted from a disc and did startup repair and then it went straight in!

 

I noticed that I no longer have a UEFI partition, or a system reserved partition. Instead I have a random 128MB partition as the F: drive letter on my SSD and a 261MB unallocated partition. My secondary HDD also has a random 185MB unallocated partition. Running system information showed the BIOS mode is Legacy! I have no idea how this has happened! I have never ever converted from UEFI to Legacy!

 

Also in disk management if I right click the SSD, it says "convert to GPT" as greyed out implying it has also been converted to MBR in the process.

 

Please can somebody explain how I can convert it back to UEFI, convert it back to GPT, and get the necessary partitions back so I can boot up and undo what Windows has done?

 

Thank you in advance!

[Guest]

Boot from install media, open a command prompt and see what the results are from:

mbr2gpt /validate

(Find the windows drive and cd into it first)

[Guy Marshall]

2 minutes ago, Den-Fi said:

Boot from install media, open a command prompt and see what the results are from:

mbr2gpt /validate

(Find the windows drive and cd into it first)

Thank you for the quick reply! I have never heard of that command before, and this is what it showed:

[Guest]

1 minute ago, Guy Marshall said:

Thank you for the quick reply! I have never heard of that command before, and this is what it showed:

You need to be in the drive windows is on. (i.e. c:\> mbr2gpt /validate)

Try C:\ then type dir to list the contents of the directory and see if that is where Windows is installed.

Rinse repeat with other letters if you don't see it as C:\.

[Guy Marshall]

6 minutes ago, Den-Fi said:

You need to be in the drive windows is on. (i.e. c:\> mbr2gpt /validate)

Try C:\ then type dir to list the contents of the directory and see if that is where Windows is installed.

Rinse repeat with other letters if you don't see it as C:\.

Silly mistake from my part! I ran it from C where windows is and it shows the identical message!