Method 1. Use bootrec/bootsect to fix UEFI in Windows 7
1.2 USe bootsect to fix Windows 7 UEFI
Method 2. Use diskpart/Automatic Repair to fix UEFI in Windows 10/8
2.1 Use diskpart to repair Windows 10/8 UEFI
Insert Windows 10/8.1/8 installation disk or installation USB into PC > Boot from the disk or USB;
Click Repair your computer or hit F8 at the Install now screen;
Click Troubleshoot > Advanced options > Command Prompt；
Type below command and hit Enter each time:
diskpart
DISKPART>
sel disk 0
When the message “Disk 0 is now the selected disk” shows up, type:
list vol
diskpart will now show the full list of volumes on your PC, find UEFI volume from the list: UEFI partition will be on Volume 2.
Type below command and hit Enter each time:
sel vol 2
assign letter=G: Note: G shall be a unique drive letter which cannot be already used;
When the message “DiskPart successfully assigned the drive letter or mount point”, type below command and hit Enter each time:
exit
cd /d G:\EFI\Microsoft\Boot
cd /d G:\Boot\ or cd /d G:\ESD\Windows\EFI\Microsoft\Boot
Note: G is the drive letter you signed to UEFI partition and remember to replace G with UEFI’s partition letter.
bootrec /fixboot
ren BCD BCD.bak
bcdboot C:\Windows /l en-us /s x: /f ALL Note: c:\ is the drive where Windows 10/8.1/8 is installed on.
You can also run: bootrec /rebuildbcd > hit Enter;
Type: exit in Command Prompt > Restart PC.
更多其他修復 Window EFI 的方法
https://www.easeus.com/partition-manager-software/fix-uefi-boot-in-windows-10-8-7.html