Hard disk Not found

Hi,

After going through various discussions on this topic, it seems that none of the discussed topics are really relevant to what I am facing.

Here's the problem.

If I keep my laptop(DELL XPS M1530) running for a long period, say overnight, i generally(not always) find that the system issues a "Hard disk not found" msg. At this point if I run a diagnostic, in BIOS under the physical drive label there is nothing. It shows {none}.

If I reboot my system everything works fine. Now I am unsure whether this is a serious problem and there is a fault in my HDD or it can lead to a problem later on.

Thanks,

Prad