as you may know after 2002 there are 2 options there to boot your computer.
option 1= legacy bios which is with us from 80`s
i`m not going to enter the detail on how these two work. just to make long story short if your computer can boot in UEFI mode it will boot extremely faster comparing to Legacy.
if you change boot mode from bios to UEFI, your OS will not start and you have to reinstall your OS in the new environment (UEFI)
here is the method which allows you to do this without losing any information or reinstalling OS.
first thing first. see what your boot option is ( Legacy or UEFI)
there 2 ways to do this.
1. when your computer booting up if you don`t see info about your H.D.D s , ram BIOS ver ets and you jump right into windows after few second you mostly using UEFI mode and you dont need this tutorial anymore
2. in cmd or RUN type : msinfo32 if you see bios mode is set to legacy continue and if you see it has been set to UEFI happy days.
in case the boot mode was set to legacy in or order to get a faster boot u have to change it to UEFI mode.
see if you have windows installation disc if you don`t have it
you have to create a system repair disc first before you move on.
download this program :
unzip it, run CMD with administrative privileges go to the folder where you unzip gptgen. and type this command :
gptgen.exe -w \\.\physicaldrive0
this will change change guide partition form MBR(legacy) to GPT(EFI)
"0" is the number of hard drive which OS is installed on it. you can check it here :
computer management> Disk management
note that the time you run the command above you wont be able to boot into your windows until you finish the whole process.
-after you done that restart your system and go into bios setup.
change booting mode from legacy to EFI insert windows installation or repair disc into your DVD/CD rom press f10 and exit setup.
-Choose language and preferences, and then select Repair Your Computer -> Troubleshoot -> Advanced options -> Command Prompt
-type these commands and hit enter :
select disk 0 (0 = number of HDD with OS on it)
select partition 1 (use the largest partition in size)
shrink minimum=200 desired=200
create partition EFI
select partition X (X=number of partition you just created (size= 200 MB))
format fs = fat32
assign letter b:
cd /d b:\EFI\Microsoft
bootrec /fixboot (if you get some error skip this part)
bcdboot c:\windows /l en-us /s b: /f ALL