"SATA primary drive 0 not found"
 

I have a Dell Optiplex GX2700, P4 2.8Ghz, 80GB HDD, with a A04 BIOS, running WinXP Pro. My dilemma is that two days ago my PC just stopped working, what I mean is every time I start the PC up I get a message telling me "SATA primary drive 0 not found press F1 to continue or F2 etc, etc...". Now the thing is I did exactly that I pressed F1 and at first the windows xp logo along with the loading bar came up, but it stayed "loading" for several minutes until I was prompted to a blue screen where a message which read; physical memory dumped and that I now needed to find my "system administrator" for further assistance and that's where I am presently. I did not build this PC or have installed any new hardware or anything like that, it just started doing this out of the blue, from the many other posts I have read I am assuming that my HDD is gone but how can I be absolutely sure if it is indeed the HDD? And just in-case it isn't readily apparent I now pretty much nothing about building PC's or installing any type of hardware, so if someone out there can help me out with advice as to where to start, I would greatly appreciated it.

P.S. I bought this PC refurbished from a company that upgraded all of their systems so I don't even have the WinXP cd's or any other cd's for that matter.