hard disk sounds out of PC speakers

I am assuming this is the sound card speakers, and not the PC speaker.

This does not sound like a device driver/comflict/configuration/software  problem because of the variety of devices involved, though this is not totally impossible. It sounds more like an electical problem on the sound card or possibly the powersupply.

If the sound card has an electrical component failure or another failure or fault,  you can hear the activities of the system that require a lot of current because the amplifiers on the card do not have good noise immunity with the failed part (for common mode noise rejection).  The CD-ROM and disk drives use a lot of power when moving the heads or changing the drive rotational velocity in the case of some CD-ROMs.

It is also possible that the speakers have a short that is causing current to flow through the ground to the sound card and the case of the machine.  See if the sound is still there if the headphones are used.

If your power supply output is going bad and the power supply is not giving you a clean noise-free output it may not be responding to the load changes caused by the drives and the sound card is amplifying the noise.

I know this is not a very helpful  answer as far as solving your problme, and it may be hard to troubleshoot unless you have some spare parts around.

If you have any questions, ask.

RoseFire

what I suggest you is to change the cables of the sound card. and hardrives. make sure you case is ground. try this with new cables.

gabber,
The flat ribbon cable is unshielded and can radiate pulses traveling on it to your soundcard's sensitive audio amplifier.
Simply move the IDE data cable away from close proximity to the soundcard.
If thats not possible, place the soundcard in another slot, further away.
Regards,
Ralph

I've tried to move the data cable away from the soundcard, but that didn't help and was also hardly possible..
Funny thing is that this problem came up suddenly, without moving the P. And Compaq doesn't know the solution either......

If you do not have an external audio amplifier connected to the soundcard's output jack, (which can cause this problem) I think the problem is internal.
Apparently the audio input circuitry on the soundcard has failed.
Either that, or a de-coupling capacitor on your motherboard/IDE controller has.
Try a substitute soundcard.
If the problem continues, I think your only recourse is to replace the motherboard. (or IDE port, if it is separate from the motherboard.)
Let me know what you find.
Regards,
Ralph

Another thing to check is to isolate by removing everything connected to the soundcard except un-amplified speaker. (CD-ROM audio input cable, possible modem audio, or a microphone that may be connected.)
Ralph

Gabber try my suggestion in changing all cables and grounding the case properly. this might be the solution.

Gabber, as a test, go into device manager and remove the sound card and all of the devices associated with it, but don't reboot. So check and see if those sounds remain. If they do, it's an electrical problem. By remove the device in DM, you have removed the drivers that drive the card, thus.. no sounds should be generated.

Problem solved!!!
I removed the soundcard (drivers and hardware). Reinstalled everything and everything was OK. Thanks everyone!
Still don't know the root cause, but what the heck.

gabber,
Glad to hear you got it going!
You should now invite dew_associates to propose his answer for you to grade.

Very good Dennis!  (I guess I just couldn't get hardware off my mind.......)
Regards,
Ralph