The functionality for search file contents is available via the windows search tool. You can choose to search for files containing certain text. AutoCAD 2010 has an iFilter dll that allows windows to index dwg's. The problem we had was it wasn't installed correctly out of the box. Ran across a known issue in the documentation for Update 2 that just came out describing how this functionality was broken by update 1. The fix is to copy AcUt.dll from your "C:\Program Files\AutoCAD Map 3D 2010\" folder over to the "C:\Program Files\Common Files\AutoDesk Shared\ AcDwgFilter\" folder.
We're running XP and this fixed the windows text search for us. The problem we're having now is that it won't find text in Dwg's saved to the new 2010 file format. Don't know why that is. I'm searching for a solution on it now.
Hope this helps.