Thanks for explaining to me the fact that I need to be more specific.  As for the speaker model, it's the one that came with the machine and says Dell DS501 on it (it is a silver strip that mounts under the monitor).  As for outlet/plug and strip, I'm referring to surge protector (which I called a strip).  The outlet is where the electrical plug for the adaptor (the term Dell used to describe what the "wire" from the speaker goes into) plugs into the surge protector.  The problem is where the electrical plug goes into the strip - that's where the high pitched noise is when the speaker is turned off.  That was the first speaker that came with the machine.  The replacement speaker does not emit such a noise, but the speaker does not work at all.  I plan to call Dell yet again to see if they can resolve this issue and I appreciate any feedback others can supply.

Yes I am having the same the problem with the loud humming sound.  I also have had two sets of the monitor mounted speakers AS501 and both pair hummed.  After several hours on the phone with tech support they thought that it was the low quality of the speakers and that XPS was to powerful for them.  So I just received a new set of Phillips surround sound speakers and guess what they do exactly the same thing!!  I took the monitor mount speakers to work and tried them with my Dell there and they worked perfectly...so I think that the problem is either with Vista or the XPS.  I have asked Dell to send out a tech to my home to fix the problem...no reply yet from them.

I have this exact same problem.  The buzz is the worst while the computer is restarting.  Once the soundcard (X-Fi ExtremeMusic) kicks in, it is lessened, but it's still there.  When I use on-board sound, the buzz is unbearable.  I also have the sound bar that connects to the bottom of the monitor.  Any ideas?

After spending another hour on the phone with tech support...this is what they had me do:

1. Plug the speakers in the front jack where you would plug headphones in.  They worked!

2. Plug a set a headphones into the jack at the back.  They worked!

 

So they think that there is some sort of grounding problem with the computer since the headphones worked in the back (not plugged into electricity).  This doesn't really explain why the speakers worked in the front but not in the back.  A Dell tech is coming out to my house to replace the mother board!  They have not come out yet but I will post the results to let you know what happens.  Cross your fingers.

Dell tech came to house and switched out the motherboard and the speakers are working perfectly!  Hope this helps.

Thank you for reporting back.  This is very helpful.  I will try the headphone switching technique and see what I come up with.  They sent a tech out to your house?  Do you have the full complete care coverage?  Thanks.

Yes they came out to the house.  When I purchased the XPS 410 it came with a 1 year at-home warranty service.  Good luck.