I strongly suggest that you try GOG Support instead. ;)

Jokes aside, I see you've contacted us before, about a billing issue, but not about the technical issue with Icewind Dale. If we find out what kind of PC you are running, we might be able to help.

Our games work well out-of-the-box on typical PC configurations, but with PCs you can get a virtually infinite combination of hardware, software and settings, and some of them are bound to cause issues with some games.

Not necessarily. nForce is MB chipset, not GPU. It can run two cards in SLI, but it doesn't mean that OP has them.

On the other hand, you are correct ;) Dell XPS 630i comes with 2x ATI 4850 and the error is probably caused by dual card.

I have yet to find an older title that works better with SLI than without ;)

Here, you can fill this:
http://www.gog.com/en/support/contact/technical_issues_with_games/icewind_dale_complete

You don't have to pay our support, it's our job, but it would help if you wrote us directly.

The only support ticket that I could find was the one you sent 2 days ago, about some billing issues. I responded yesterday. There is, however, no ticket about any technical issues you're experiencing with this game. Have you sent us two support tickets, or just that one?

We are still missing support ticket describing your problem, especially DxDiag

http://www.gog.com/en/support/contact/technical_issues_with_games/icewind_dale_complete

^ Here, under 'Hardware information' you can find instructions how to save and send DxDiag report. Could you please send it to us?