Hi there everybody!
I decided to finish a Gothic session I had started almost 4 (yes, four) years ago. I installed Gothic from my CD's and loaded the last save only to see it's completely unplayable due to the heavy stutter and texture corruption and crashes.
So I decided to buy it from GOG seeing as their games are 100% Vista compatible as they claim. Well, just installed and tested and it does the exact same thing.
I'm running it on a Dell Inspiron 1520 notebook with these specs :
Intel Core 2 Duo T7300 2.0 Ghz
nVidia GeForce 8600M GT 256 MB and 190.62 drivers
2 GB RAM
Windows 7 - that's right, I'm actually foolish enough to hope this game can run OK on Windows 7.
Seeing as Windows 7 is under the hood a revamped Windows Vista, i was hoping for, at least, the Vista-compatible-GOG version to work great.
BTW, I do have DirectX 9 August 2009 installed on it. just so you know and not recommend as a solution :)
This is a YouTube video describing what I'm talking about : http://www.youtube.com/watch?v=fWFXPnLUMuc
Some help would be greatly appreciated because I really like to play and finish G1 (I am somewhat of a Gothic fan, having played G2 and G3 also)

Unfortunately this is a known issue with recent Nvidia drivers (see the Game Crashes When Going Outside thread for more information). At the moment the only real solution is to wind back to an earlier driver version that works correctly with Gothic.
For reference I am running both Gothic games flawlessly on Windows 7, but the crucial difference is that I have an ATI GPU.

My 8800GT on XP:Pro (32 bit) with newest drivers has very frequent freezing issues with Gothic (and lots of other games.) It happens more in some areas (swamp, old mine) than others (forest, old camp.) The only thing that has worked for me is setting the texture detail to absolute minimum. Which looks really ugly so I only use it for the areas with frequent freezes.
Now the issue is obviously different form yours, but try reducing various graphic settings, and playing around with the Nvidia Control Panel 3D Profile for Gothic.

I also get this problem but with a Radeon 4870. I've tried reverting to earlier drivers with no luck. Can sometimes play up to 20 minutes but then the freeze happens; video freeze and sound loops a few time, have to reboot. Will try setting textures to minimum (ugh).
EDIT: I tried lowering textures to the absolute minimum and also turned hardware sound off, but still get this freeze.
P.

How about trying to revert back to an older graphics driver?