dell OptiPlex 380

Hello friends,

I just bought a new dell OptiPlex 380 when I switched on it says strike f1 to retry boot F2 for setup utility press F5 for onboard diagnostic. I have tried everything but it still cant recognized by Bios.

These are steps I have done so far.

1. changing the bios settings
2. Running onboard diagnostic  
3. changing dvd+w and HDD

can any one assist me please. I will appreciate your help .