Ah, sorry for the confusion. Just to clarify, here is the version history for MTW:

Base MTW game, released as v1.0. CA released a v1.1 patch for this.
Viking Invasion expansion released, this brought the engine to v2.0. A bug slipped through the cracks, and CA released a 2.01 patch to fix.
MTW Gold contains both MTW and Viking Invasion. Depending on the source, the engine will either be v2.0 or v2.01. The version number should appear in the corner when on the main menu screen. A separate patch for MTW Gold is available to bring it to v2.01, it's just the updated Medieval_TW.exe file.

If you want to upgrade, you can get either the Viking Invasion expansion or MTW Gold, whichever is cheaper and easier to find. Just make sure you run it at v2.01, or else your kings will die at age 56.