Originally Posted by -HAL-

I had lots of problems w/Vista, but after I tried this "fix" the game haven't crashed once..

Run the command prompt as admin
(Start > All Programs > Accessories > right click Command Prompt > Choose run as Administrator)

Enter BCDEDIT /set IncreaseUserVa 2800
Restart the computer and start the Witcher

It's recomended to set the value back to 2048MB after you are done playing the game...