This is, IMHO, Windows' best trick and the biggest time-saver of the bunch.  In short, it makes it easy to load a file into a program that it's not normally associated with.

A quick example would be a Notepad document you want to spell-check.  Notepad doesn't have a built-in spell-checker, so the usual routine would be to:

• Laboriously fire up a program with a spell-checker like MS Word
• Painstakingly open the load requester
• Achingly browse to the Notepad document
• Tiresomely load the file
• Troublesomely spell-check the document
• Backbreakingly save the file
• Exhaustedly close the program

Sounds pretty grim!   But with the SendTo feature:

• Simply click on file's icon with the right mouse button and 'send' it to MS Word
• Simply spell-check the document and that's it!

Yep, one thing you can always count on from me is a fair and unbiased review.

Let's start at the beginning:

Every file on the computer that's used by people (as referred to system files) is associated with some program by way of its file extension.  That's the program that runs when you double-click on the icon.  An ".htm" file extension opens the browser, a ".doc" file extension opens the word processing program, etc.

Note: If you aren't seeing file extensions on your computer, go to Control Panel, 'Folders', click on the 'View' tab and un-check "Do not show hidden files and folders."

The trouble arises as with our Notepad example, because Notepad doesn't have a built-in spell-checker.  So, the normal routine would be to fire up something like MS Word and then painstakingly, troublesomely (well, you get the idea) browse to the file and spell-check it.

If you'll click on any icon with the right mouse button, you'll see a 'Send To' entry in the menu.  Using the SendTo feature, you can quickly 'send' a Notepad or Wordpad file to MS Word, rather than having to browse for it in the requester.

Here are some possible uses:

• Got a file you want to move to a certain folder?  Click on the file, pull the menu down and 'send' it to the appropriate folder
   
• 'Send' sound files and songs to your audio editor or a different player than what they're normally associated with
   
• 'Send' pictures to editors and viewers
   
• 'Send' BAT, HTML, PHP and CSS files to Notepad or Wordpad for editing
   
• 'Send' raw video files like VOBs to a movie player like PowerDVD
   
• 'Send' pics and videos to a program like Media Info to obtain the technical specs of the file
   
• 'Send' image files like BIN and ISO files to ISO Buster for extracting
   
• Programmers: 'Send' files to your hex editor of choice

 
Setup

Setting up the SendTo feature is fairly easy.  First, you dig up a folder buried deep on the drive, empty it out, then copy the icons of the programs you want to 'send' things to to the empty folder.
 

Win XP:

To set up the SendTo feature:

• There are actually two 'SendTo' folders, so let's clean out the unused one first.  Open 'My Computer', C Drive, 'Documents & Settings', 'Default User'.  If you don't see it, go to the window's Tools Menu, 'Folder Options', 'View' tab, check the 'Show hidden files…" gadget.  Open the folder and delete everything inside.
   
• Go back to 'Documents and Settings', open your <login name> folder, then the "SendTo" folder.  Delete everything except any icons you want to use with the SendTo feature.
   
• Go to the Start Menu, find the icon of the program you want to 'send' files to, hold down the Ctrl key and d-r-a-g the icon over to the SendTo folder.  Drag any other icons you might want, such as Notepad, Wordpad, WinRar, ISO Buster, movie players, audio editors, whatever.  Don't forget to hold down the Ctrl key or you'll be moving them, not copying them.
   
• Close the SendTo folder (or hit the 'Back' button if you're using the single-window system) so you're back in the <user name> folder.  Highlight the icon to the SendTo folder with the right mouse button and 'Create Shortcut'.
   
  Assuming you organized your Start Menu as on the 'Start Menu' page, open up the 'Programs' folder and d-r-a-g the SendTo shortcut icon over to it.  If you didn't organize your Start Menu, just grab the icon with the mouse and drag it to a likely spot in the Start Menu for future use.

Alphabetizing the SendTo entries in the drop-down menu is kinda goofy, but this is the way it's gotta be done:

• Create and open a new folder.  Now open the SendTo folder, highlight all of the icons with Ctrl-A and move them over to the new folder.  From the View Menu, 'Arrange icons by', 'Name'.
   
• Now drag them back to the SendTo folder in alphabetical order.  It doesn't matter where you drop them, just the order they're dropped in.  It's lame, but at least it works.

Vista & Win7

To set up the SendTo feature:

First, open Control Panel, 'Folder Options', click on the 'View' tab and select 'Show hidden files…'.  Some of the folders you're going to access are 'hidden' and you wouldn't see them without this feature turned on.

There are two 'SendTo' folders on the system with stuff in them and we need to empty both:

• Open 'Computer', then the C Drive, then navigate to:
   
  Users\Default\AppData\Roaming\Microsoft\Windows
   
  Open the 'SendTo' folder and delete everything.
   
• Go back up a level to the 'Windows' folder.  Right-click on the 'SendTo' icon and 'Create shortcut'.  Drag the shortcut icon over to the Desktop for future access.  You can also d-r-a-g the shortcut icon over to the Start Menu.
   
• Now back up to the 'Users' folder and this time navigate to:
   
  (your user name folder)\AppData\Roaming\Microsoft\Windows
   
  Open the SendTo folder, empty it and close it.
   
• Go to the Start Menu, find the icon of the program you want to 'send' files to, hold down the Ctrl key and d-r-a-g the icon over to the SendTo folder.  Drag any other icons you might want, such as Notepad, Wordpad, WinRar, ISO Buster, movie players, audio editors, whatever.  Don't forget to hold down the Ctrl key or you'll be moving them, not copying them.
   

Notes:

• A few programs, such as MS Word, won't work with a Start Menu icon.  You have to dig up the actual program and make a fresh shortcut icon of the main program, then drag that shortcut icon over to the SendTo folder.  To find the location of the real program, right-click on the Start Menu icon, open its 'Properties' and look in the 'Target' box.
   
• At the bottom of the SendTo menu are a few entries that can't be deleted.
   
• Occasionally, a program will put an icon in one of the two SendTo folders during installation.  These should be deleted.

On the subject, there are programs out there like OpenExpert, which take the 'sendto' genre to a whole new level, so if you're dealing with scads of different types of files and editors and viewers and players, that might be the way to go.