Inevitably in MOSS if you are doing custom development there will come a point where you will have to generate new GUIDs for your features, lists, fields and whatever else. There is a quick and easy way of doing this from Visual Studio.

Simply open Visual Studio and go to Tools à Create GUID

Choose Registry Format and then Copy. Done and Done. Know that certain GUIDs in MOSS will complain if you have curly braces {} and some will not.

If you are more of a command-line person you can get to the same screen by typing:

guidgen

in the Visual Studio Command Window