Drives not found

I am getting the following message when I turn on a Dell Precision 360:

SATA Primary drive 0 not found
SATA Secondary drive 0 not found
Primary drive 0 not found
Primary drive 1 not found
Secondary drive 1 not found
Alert! Cover was previously removed.

strike F12 to retry boot, F2 for setup utility

Someone said the computer needed a new hard drive and an OS. My question is what is the best way to proceed. Mostly interested if I can fix this without buying any hardware.

Thanks in advance.
Thanks uawret but I am more concerned with the messages that say the drives were not found than the alert that says the cover was removed.

Thank-you though.