All tests are fine. When I hear the short beep I notice that disk has full I/O activity.
Sure, do let us know with the outcome.
If the beep is frequent, can you leave the machine in BIOS and check if the system still beeps.
Even during stress test which you are going to run, observe for the beeps.
The machine is clean. It has McAffe installed.
The sound seems to be produced by a hardware component, I suspect the hard disk. I have talked to Dell support and your technician told me that is propably the HDD.
I will do another stess test tonight to see what happens.
Strange, because another user had similar issue few days back, who eventually found out that the system is infected.
Please run an antimalware and antispyware.
Antivirus may not detect any threats, so would request you to run the above as suggested and let us know once its cleaned of them.
Also please update the bios if not done yet.