Vista knocking noise?

[dayslayer8]

i just got this weird knocking noise from my vista. The noise happens for about every 5 or 10 minutes. If u knock on ur desk 3 times in about two seconds or less then you know what i am hearing. It may be some alert or something but i dont see and messages or anything...anyone know what it is?

 

[raybay]

Could be anything... A cable bundle banging against the case or other component... failing hard drive bearing... optical drive wear or failure... Cooling fan bearing
Perhaps there are alerts that sound like knocks, but that would certainly be a new twist from the beeps of the past 22 years...
Some Vista Media Center machines are guilty of all sorts of noise...

It would be useful to know more about your sytem... brand, model, age, and configuration...