Computer crashed. No bootable disk found

My computer crashed and it says 'no boot device detected, insert system disk and press F1 to continue' I Google how to fix it and it says that I am to change to boot sequence in the BIOS.
I tried and it says they are all not present. I don't know computers very well, but this is a business computer and very important.
Can someone PLEASE help me, I'm going to cry!
