My Computer sounds like Morse code ?

[#1]

Hi
I have a strange problem, every few minutes my computer makes a morse code type sound, it only does it for three or four bleeps and then stops it does this several times and then stops,Then a couple of days go by and then it does it again.The sound does not come through the speakers but sounds like it is within the machine, I thought i might have a loose connection but cannot find one maybe someone is trying to contact me or is my computer about to explode ?

[#2]

Some software uses the speaker to get your attention as in theory the speaker is all ways on while the sound card may not be on.
Some Av us it so it could be a warning of virus activity or similar do you have any old software as in the days long ago we didnt have sound cards and all software used the speaker so any old software running could do it.
It could of coarse be the First encounter from another planet

[#3]

I am using a Dell Dimension 4300 running xp pro
The sounds are long and short beeps and they do not seem as though they are coming from the internal speaker they are more like internal electrical sounds similar to interference or old circuits running  sorry i cant be more specific but they have stopped now perhaps first contact has moved to another computer.....

[#4]

Do you have a mobile telephone nearby when these sounds occur.  I get similar noises caused by my mobile when it "handshakes" with the base station