Select the file types you'd like Google Desktop to include in its indexing and search routines. The more file types you select, the more complete record Google Desktop will have of your system. If you omit some file types and then do a search, items within the omitted file types will not be included in the search.
However, if you have concerns about the privacy or security of your computer, it my be wise to omit email, web history and HTML files from the search.
By default Secure web pages or SHTML files are omitted from search and indexing. This includes web pages like your bank or Pay Pal accounts. To turn on index and search for these files, select the check box before Secure pages (HTTPS) in web history.