I really need some help with my Hard Drive.

Here I go again. About a week ago, my computer was freezing, and getting the flashing question mark. I booted off the install disk, and managed to get things running. Then it happened again, and it started shutting off on start up. Long story short, things looked pretty haywire with the hardware and permissions test, so I have had to do 2 clean installs. Things seem to go well for a few days, then it starts acting up and freezing. Right now I am o.k. I have disconnected everything except the internet cable and the mouse and keyboard. The only programs on the mac are the ones from the install disk. I haven't loaded all my back up files yet, so it is in relatively pristine condition from the install disk. I ran the permissions repair and it was complete, I verified the disk and the Mac HD appears to be o.k. However, when I run the hardware test off the install disk it reports an error:
4MOT/1/40000003:HDD-1344

Second test reports error:
4MOT/1/40000003:HDD-1331
I called my apple rep, and he says it's probably the hard drive. He didn't seem to know much of anything. Had the attitude that let's just try a new hard drive without looking at any of the test results. My question is this, does anyone know what the error message means, and could the errors be from something other than a bad hard drive. My computer is only 13 months old. One month off waranty. I find it hard to believe that my hard dirve is fried. Any suggestions. Although I have learned a lot about diagnostics this past week I am still green at this stuff, so please keep it in simple terms. Thanks