No Boot Device Found

1) Check Cables:

• Turn off PC, open case, firmly push in all power and data cables going to your main hard drive/SSD. 
• Close case, restart.
  

2) Fix Boot Order in BIOS:

• Restart PC, repeatedly tap Del or F2 (or F10/F12) to enter BIOS/UEFI settings. 
• Find "Boot Order" and move your Windows drive (or "Windows Boot Manager") to the top. 
• Save & Exit.
  

3)Try Boot Mode Switch: 

• In BIOS/UEFI (same place as above), find "Boot Mode" or "UEFI/Legacy."
•  If it's UEFI, try Legacy. If Legacy, try UEFI. 
• Save & Exit. (Change it back if it doesn't help).
  

4)Reinstall Windows (Clean Start):

• Boot from your Windows USB/DVD. At the drive selection, delete all partitions on the main drive, then install Windows cleanly. (

WARNING: Erases everything!)