Windows 7's search box can quickly find apps and file names, but it could be more helpful. Make it so by enabling Windows to always index the contents of your files, so you can find your shopping list by typing "tomatoes".
By default, Windows 7 only indexes file contents of Word documents, text files, and other known data types in the locations you've approved for indexing, i.e. regular access and faster search. By hitting Alt on an Explorer window, choosing Tools->Options, and enabling universal content search in the Search tab, you're on your way to knowing where everything readable is at all times. This move will of course make indexing take some time and might slow down your search depending on your hard drive's contents, but it also makes Windows 7's search box far more useful.
Hit the link for a full walkthrough of enabling universal content search.
Windows 7: Always Search for Contents Inside Files [Tech-Recipes]