How to Convert GPT to MBR (or MBR to GPT) without Operating System?
Geeks - It is not possible to convert between GPT and MBR without an operating system. GPT (GUID Partition Table) and MBR (Master Boot Record) are two different partition styles that are used to organize the data on a hard drive. In order to convert between the two, you will need to use a utility that is built into the operating system, such as the Disk Management utility in Windows or the diskutil command in macOS.
If you are trying to convert a hard drive that does not have an operating system installed, you will need to first install an operating system and then use the appropriate utility to convert the partition style. Keep in mind that converting a hard drive from GPT to MBR or vice versa will erase all the data on the hard drive, so make sure to back up your important files before proceeding.