No bootable devices found

Step 1 : Check if your harddrive/SSD is getting detected or not, Run ePSA : F12 > Diagnostics 

Step 2 : Add Boot Path manually 

Step 3 : Reinstall OS > You can use F12 > SupportAssist OS Recovery for that

Welcome to the Dell Community  @Yan Paing Tun 

To better assist you, the members and I would need the exact model number of your laptop/desktop???

1. Go into your BIOS.

Power-on the system and start tapping the F2 key to enter System Setup.

2. In Windows:

Hold down the” Windows “key and tap the “R “key.

Then type msinfo32 and hit enter.

Best regards,

U2

PLEASE DO NOT POST ANY SERVICE TAGS!!!