External HDD enclosure causing nasty static noise

Hello all. I'm hoping some of you kind folks can help me with a little problem I've got. You see, I recently bought a cheap Ebuyer Value HDD enclosure (in actuality it appears to be the product of some company called SafeCom), and it seems that whenever it is plugged into my computer, a horrible static noise is made by my speakers (also plugged into the same computer, which for the record is an Acer laptop). If I disconnect either the speakers or the HDD from the computer, the noise ceases. This all happens regardless of whether the HDD is connected by USB or Firewire.

After tinkering around a little bit with the thing, I eventually discovered that if I unplug both the USB (or Firewire) cable and the speakers' audio cable from the computer, and touch them together, the same noise is made from the speakers. So it is as though somehow a connection is being made from the HDD plug to the audio plug on the inside of the computer, while both are plugged in.

I haven't had any trouble with other USB or Firewire devices however, so this seems strange. Curiously I have also noticed that this only happens with the speakers I have plugged in. If I instead plug in my headphones, no noise is made through them. Not even if I do the 'touch the plugs together' thing with them.

The basic issue is that I don't know who or what to blame. The cheap HDD enclosure? The speakers or their cables (which incidently are sort of permanently attached to the speakers)? Some bizarre wiring inside the computer?

Should I send the HDD enclosure back, or what? I intended to have this drive plugged in at all times, which is clearly not going to be an option while this problem exists.

Thanks for your time. :)

ha my flatmate has exactly the same issue with his imac. its so wierd i cant get my head around it. the really daft thing is that the cables to his speakers dont even have to be connected to the mac for the hum to happen. its like you can hear the disk spinning up in audio through the speakers..... wirelessly. being an imac i thought wifi??? switched it off but no change. if there's anyone who can work this out im sure it would be appreciated!