I have a client with this issue and I can not seem to find a solution. They were trying to search for files under the Start Search Option and it would not find them. I went to the Index Option in Control Panel and it said the service was not running. So we went to services.msc and tried starting it then got the error -2147218170. I search the net found plenty of docs for Vista one being http://www.vistax64.com/tutorials/85803-index-windows-search-service.html but none seem to help with Windows 7. He has no idea when it stopped. Any help or ideas please.

Try resetting and rebuilding the search index. See this thread: Windows 7 search won't start - system error 2147218170 - Microsoft Answers ...especially the last response, linking to the following URL: SevenTier IT Solutions: Windows 7- Windows Search Service does not start Ramesh Srinivasan | The Winhelponline Blog Microsoft MVP, Windows Desktop Experience