I tried using MBR2GPT on my Windows 10 Professional computer. It errored out somehow. I did not catch the error. But now the computer will not boot at all. It says there is no operating system. I would like to go back to a MBR drive and be able to boot into Windows 10 again with a MBR hard drive. Does anyone know how this is done and accomplished? When I try to boot up, it says there is no operating system. MBR2GPT must have done something to the drive, partitions, master boot record, or something else I don't quite understand. I have not been able to find any details on exactly what MBR2GPT does to a hard drive. I do know there are 4 drive letters now that show up in File Explorer. A System Reserved drive letter, my Windows 10 drive letter, and two more drive letters that have no descriptions on what they are. Thanks in advance for your time and help with this.