Google can let you restrict your searches to only certain file types. This can be very helpful if you're looking specifically for file types, such as PowerPoint, (ppt) Word, (doc) or Adobe PDF.

To restrict your search to a specific file type, use the filetype: command. For example, try searching for:

hotel filetype:doc

You can use this same syntax with Google Desktop. To search for that forgotten widget report, try:

widget report filetype:doc

By default GooglePowerSearch gives you a dropdown list for searching by file type.