i have dell optiplex 780 which was working perfectly fine, suddenly the device stopped working and when ever i try to start it up, it shows me this message:
Drive 0 not found: serial ATA, SATA-0
Drive 2 not found: serial ATA, SATA-2
Alert! Failed to detect one or more drives during POST.
Strike the F1 key to continue , F2 to run the setup utility , press F5 to run onboard diagnostics

when trying press any of the f keys, nothing happens so i thought there some thing wrong with my keyboard but i tried with another two different keyboards but it still no key is working.

also when i tried Pressing when the Dell™ logo appears to initiate a one-time boot menu, after the menu appears all keys will not respond again.

can someone tell me whats the problem and help me with this?

device os : win xp
BIOS version A03