Windows uses an index to perform fast searches through the Windows Explorer interface. On my Windows 7 system, I want to be able to search using the interface in the upper-right hand corner of the Explorer window. The index and search normally work fine.
This "system index" is what is affected by the Indexing Options in the Control Panel. I have it set to index all local drives. On my Windows 7 system index, I have about 800k files. Every few weeks, the index appears to be erased and all items are re-indexed, which takes a few days.
Why is this happening and how can I fix it?