In Windows, Search and select “disk management” In graphical view, right click on the far left box next to where the Bootable C:Drive is installed, which should be disk 0 (but not always), and then select “Properties.” Then select the tab marked “Volume.” Determine if this boot drive is GPT (UEFI) or MBR.

In Windows search box next to the Start button (bottom left corner), type cmd and when “command prompt” results as a search hit, then Run “Command Prompt” AS ADMINISTRATOR!

mbr2gpt /validate /disk:0 /allowFullOS

mbr2gpt /convert /disk:0 /allowFullOS

After conversion, remember to boot into CMOS Setup and switch from Legacy MBE to UEFI in the Bios Setup, or your system will not boot to the GPT boot drive.