I sometimes get horrible cackling sounds while playing, it only happens while in towns.
It sounds to me as if one of the music tracks has corrupted, I reinstalled the game after re-downloading it and no I didn't skip the file integrity checks, the problem is persisting, is there a solution?

Dang, I didn't see someone else had posted about this already:
http://www.gog.com/en/forum/divine_divinity_series/sound_crackling
It just goes to show the power of Google!
Well, i'll set the processor affinity to one core and see how that goes...

I'm running on a Pentium 4 with hyperthreading, and I'll get the same or similar effect for a literal second sometimes. It happened with my CD copy as well. Mine wasn't enough to cause a problem though. I'll have to try runfirst and see if it goes away.

RunFirst will only work on Dual Core CPU's so It won't help your Pentium 4 since it is a single core processor.

I would suggest that you lower the hardware acceleration slider for your sound card (the windows slider for your card, see attached image). In some cases turning it off is required. This usually fixes the problem on most older systems. Also, make sure you have the latest drivers for your sound card. . . =)

He said his P4 has HT. I have a P4 with HT in another computer, and Windows treats it as two processors. Maybe runfirst could help him.

EDIT: Errr, more correctly, Windows treats it as two cores. I said two processors... >_>
Makes no difference here though, just clarifying it.

Hummnn, my bad. Does the P4 HT allow you to set the affinity for the CPU? See attached image.

Yeah, it allows for core affinity. I think it treats it as a dual-processor system in that regard.

RunFirst should help with the sound issue in this case.

Better, this worked for me:

Right click Divine icon and click properties.
Change the target to:

C:\Windows\System32\cmd.exe /C start "" /affinity 1 "C:\Program Files (x86)\GOG.com\Divine Divinity\div.exe"

Change the paths of your windows/game.