bengeddes: You don't need to be trying to patch the game if you have the GOG version - this is the general rule of thumb for GOG. You should state what version you have in your first post so people don't get confused trying to give you patching advice. I also can't believe someone is giving you patching advice without first asking what version you have.
So first thing is, get rid of any patches you've got, and just do a clean install of The Witcher.
Next, if the adventures aren't showing up in-game, check the proper folder to see if they are installed:
The adventures are not located in Documents\The Witcher (I don't think they're there in any version of WIndows). That's where the
saves are.
Adventures are in C:\Users\Public\Documents\The Witcher\
These are the file names:
m1_module.adv
m2_module.adv
So, you need to check inside C:\Users\Public\Documents\ and see if by mistake there are TWO folders called The Witcher there. If there are, copy the files listed above from one folder into the other.
Bumping old thread to say: THANK YOU. Running on Win7 64-bit at least, this is the solution. I am running Steam version of the game. Creating the folder path in "Public" and placing the .adv files in there worked!