If you Google for "geocoding virtual earth site:microsoft.com" you will get quite a lot of hits...

If you are going to use Microsoft Virtual Earth, it can do the geocoding for you; see the MSDN article on Getting a Precise Location in Virtual Earth. You can also use MapPoint Web Service to do the geocoding and display the results in Virtual Earth, see MSDN's article on Precise Geocoding with MapPoint Web Service and Virtual Earth.