If you start to notice that your index becomes sluggish in performance or even stops working, you can rebuild the index and regain the performance you seek. To rebuild the search index…
1. Go to the Control Panel.
2. Select System and Maintenance.
3. Select Indexing Options.
4. Click the Advanced button.
5. When the UAC prompt appears, click Continue.
6. Under the Troubleshooting section, click the Rebuild button.
7. Click OK when the confirmation box appears.
8. Click the Close button to close the Index Options window.
It will take a little time for your system to rebuild the index, Search will not function until the rebuild is complete.