I found that something is making Vista forget its Indexing locations.
If (for example), I set it to index the C drive, and then some time later on I do a search anywhere on the C drive, I get a message that the search is not included in the indexing, and I get a prompt to add it to the Indexing Location. I went to Indexing Options and found that the Included Locations that I had set had gone.
I finally traced it back to jv16 PowerTools 2006 Registry Cleaner.
I just thought I would alert you to this.