Google Desktop Search is out of beta and has been officially launched. It is much improved and now searches PDF files. Support for Netscape, Firefox, Mozilla and Thunderbird has also been added. For Open Office and Star Office users there is a plugin at http://desktop.google.com/plugins.html
As well as switching off cacheing and indexing of secure web pages, such as your online bank statement, you can also switch off indexing of password protected pages. All documents still remain in the cache after you have deleted the original unless you follow the remove instructions at http://desktop.google.com/features.html#remove
It is a rather tedious process and isn’t straightforward. There is a danger that you could miss files, especially individual emails.
Personally, I’ll stick with Yahoo Desktop for the time being.