Hi,
it's all said in the subject.
After I start the game the screen went black and nothings happens except that i can hear a music playing.
No Intro movie, no game.
Also it's very very hard to come back from that state to the windows desktop....trying serveral time ctrl+alt+del and nothing happens. Alt+tab does the thing after a 100 replies.
My Hardware:
Core2Duo Quad 9650
4 GiB Ram
Radeon 5870
Soundblaster X-Fi Music Extreme
P45 Platinum Motherboard
Anyone a idea or suggestion?

I'm on XP.
Sound level adjust don't help and caps lock is not enabled.

Just to be clear, it's not the sound level adjust as in volume adjust.
It's the level of sound hardware acceleration.
Start > Run
type dxdiag, click ok, switch to the Sound tab.
The slider to adjust the level of hardware acceleration is there.
If that's what you did, the other suggestions i have are the usual ones
- make sure graphics drivers and directX files are up to date
- make sure your AV isn't interfering with launching the game

I know that you meant the hardware acceleration level.
I tried various beta drivers for the 5870 and the official 9.10.
All failed.
AV is always out when i try to begin playing.
At least I think it's a gfx-driver problem. The 5870 is just to new. Maybe with Cat 9.11 or 9.12 the game-support is better and more stable.

Have you run the game configuration first? The link (for me at least) is start -> programs -> gog.com -> Divine divinity -> configuration.
The first time I started the game I got a blank screen and problems, then I ran the config, set the res, and it worked fine.

My game just crashed for the first time and it wouldn't run without running the config tool first, so you might be on to something there...

I have the exakt same problem here.
I bought the game today. I installed it under Windows XP SP2 DirectX version 9.0c.
When I start the game I see the loading screen blink: the loading bar goes to ~30% then it goes black, then it comes back and loads to ~50% then it goes black again. Then i comes back and load to ~60% and then goes totally black. But the menu? music slowly fades up. But then: nothing. All black. I can hear that I can press the mouse key or the ESC key.
I don't have a clue what to do?
I have a Laptop Fujitsu Siemens with a X1800 mobility radeon with the Omega 4.8 drivers.
Gee, setting the hardware sound accelerator to "Standard" really helped :-)
Thanks alot for the advice!

I hear this works for a similar problem on Vista (same problem, different game), might even on XP as well. I don't have the problem so I can't test it. Thought it might be worth a try since you seemed to have everything else working properly.
Go to [your drive letter]\:Program Files\GOG.com\Divine Divinity and right click the Divine Divinity folder. Click Properties and than the Security tab and check mark Full Control for everyone.