The thing about IRQ's is that they are an INPUT to the system.

Conceptually, the CPU is the computer and EVERYTHING else is a peripheral - including the RAM...

Any peripheral that wants CPU time must generate an interrupt to catch the CPU's attention... So, if a peripheral is OUTPUT only then it will not need to generate an interrupt even if it has an IRQ assigned. Some device drivers can even be configured to make the CPU poll the device rather than depend on an interrupt.

Your video display is an output device. A sound card is (usually) an output device. Exceptions with sound cards would include those with onboard synths - many of these use the CPU and system RAM to power the synth and store soundfonts - these cards would need an IRQ.

In Johns case, the Creative PCMCIA card would use its IRQ. The Realtek that's on board probably would not (though I could be wrong here). I'm not certain about the USB Exitgy but it probably uses the IRQ as well.

So, 2 devices that probably use the IRQ and 2 that probably don't. As long as the drivers for these devices chain the IRQ handlers properly there should be no problem BUT if there are any issues with the drivers then I would expect things to misbehave. Ditto if there are BIOS problems 'cos there are basic IRQ routines in the BIOS that are called by the OS (including the drivers).

Once upon a time you COULDN'T share IRQ's. These days it is best practice to avoid it but if you must then try to choose low bandwidth devices to share. I.E NOT the HDD controller or your NIC (Network Interface Card) Unfortunately you don't always have a choice.

After all the above waffle, I notice that John had good results with an external USB drive - funny that it still shares the same IRQ thats in question. this makes me feel confident that the real problem is most likely not an IRQ sharing issue but rather points straight back to the HDD I/O.

John, with that in mind, has it always had this problem or has it just developed recently and if the latter then what changed? If you don't know of any changes (particularly to software or additional hardware) then I think I'd have another look at the HDD (either full, fragmented or failing). If its always had the problem the I'd suspect the HDD is a low performance one.

--=-- My credo: If it's worth doing, it's worth overdoing - just ask my missus, she'll tell ya laugh --=--
You're only paranoid if you're wrong!