When you upgrade to Microsoft SharePoint Server 2010, some of the new SharePoint Enterprise Search Web Parts are missing from the Web Part gallery for upgraded site collections.
The following are the missing Web Parts:
  • Refinement Panel
  • Related Queries
  • People Refinement Panel
  • Dual Chinese Search
This topic describes how you can add these Web Parts to the Web Part galleries of the upgraded site collections.
Another post about this with more detailed problem information