When I go to the darkmere swamps , I can't see anything. The screen is all white and I can still hear sounds and music. Can I somehow stop this from happening? Can I change something in the video settings to make everything visible?

Again, which card you are using? this can help us determine which kind of problem is going on here.

I think I have a direct 3D card. Somebody told me before that I should lower the textures or something. How do I do that?

Why don't you try to running the game in OpenGL? There are some cards which had problems with D3D.

If you use onboard integrated Intel graphics, you might want to upgrade to a $30 graphics card, it's about a 1000x better.

I used to have problems like that. I then tried running the game in OpenGL and it worked fine. And listen to Ramborc about upgrading from an Intel card (if you have one). Because my computer has an Intel Extreme graphics controller. It a hideous card, but I can't really upgrade the computer.. I suggest trying it in OpenGL.