Rebuild MBR - Missing System Partition

Windows 10 old Motherboard cratered a while back. While troubleshooting I'm afraid I have made it worse, although not sure if that was really possible. I would like to reinstall without loosing my installed programs etc. I have backed up the drive in question.

Windows 10 WILL NOT BOOT. Will not repair, ran through multiple attempts with self repair and using installation media. I was following How to Restore Deleted EFI Boot Partition in Windows 10/7 | Windows OS Hub only to find out that the disk is not setup as GPT but Basic.

Does anyone know of a way to restore/rebuild the MBR and partition on a basic BIOS based installation? I have access to a newer NUC as well and can run the drive in that too.

I have attempted to follow fixMBR/RebuildBCD procedure with no positive results. Failed doing that before trying the deleted EFI partiion procedure above.

Any suggestions?

Welcome to the forum. Can you get a screenshot from disk manager so we can see or simliar from partitioning software its knowing how its setup and what mode is set in the bios for it

Boot from the Windows 10 Installation USB flash drive. At the first screen, press Shift + F10 to open a command prompt. Run:
diskpart
list vol <- judging by the sizes listed and possibly the label, figure out which one is your installed Windows partition, also note which drive letter it looks like the USB flash drive is assigned
select vol # <- replace # with the actual volume number of your installed Windows partition
active
exit
X: <- change this drive letter to the drive letter of the installation USB flash drive.
CD \boot
bootsect /nt60 C: /force /mbr <- change C: to match the drive letter of your installed Windows partition you found in diskpart
bcdboot C:\Windows /s C: /f ALL <-Change both C: to match the drive letter or your installed Windows partition
exit

Exit setup by clicking the red X in the upper left corner of the Window. Remove the USB flash drive and reboot your computer.

Following NavyLCDR's recommendation:

After i selected Vol#, and hit active it errored out and said that I need to select a partition. There are three partitions under that volume, assuming I select the active windows partition the active completed then. I went through the rest and it still errored out when I rebooted. Two reboots and two different errors (see attached)

I am using my NUC not my legacy BIOS based motherboard right now. I can switch it back to the legacy, was just using the NUC out of convience. I have also attached a screenshot of my partitions.

Tell us the story of the HDD. It is set as dynamic data.
What Are Basic and Dynamic Disks – Features, Differences, Conversion
Was on the computer it was originally installed, also another disk?

Originally the hard drive was a basic drive, installed in a computer with an Asus mother board P5BDeluxe. It got currupted while in that computer. I kept it in there troubleshooting it until I suspected that it may be a board/memory issue. So recently I put it in the Intel NUC for ease of troubleshooting (the other computer is fairly large and was taking up desk space while working on it.

The drive is an SSD, and I've run chkdsk on it and no issues found. Originally it was a basic drive, until one of my troubleshooting steps upgraded it to dynamic.

The original problem was the OS failed to boot. Autorepair did not work on it and it appeared to be in a repair loop, it kept booting and saying that repair couldn't fix it. I attempted to repair using external USB as well, no luck. I'm afraid my attempt to fix it may have made it worse, however considering it wasn't repairable by the windows media, or self repair, my limited options were to keep trying or start over. I would like to keep the programs/data intact, I can retrieve the data from the drive, but would rather not have to reinstall the programs if possible.

I followed the symptoms down a few ratholes, including BCD rebuild, bootrec /rebuildbcd and various steps around that. Eventually I found this at Microsoft: https://answers.microsoft.com/en-us/...3-cc275e1d9fbf because my bootrec found 0 installations.

So that is a bit of the history of the drive. I can put it back in the BIOS based Asus PB5Deluxe which is where it will go back once it is functioning again.

Does it only has data or also an OS on it?

Both data and OS.

As far as I know, you can't boot from a dynamic disk. You're going to have to convert it to a basic disk.