Installing Fonts in Windows

In order to be able to use a font in Windows, you need to:

1. Copy the font file in the Fonts folder of Windows (optional).
2. Activate the font resource in Window (mandatory).
3. Register the font in the Registry for permanent use. If this registration is not done, the font is temporary and will go away when Windows is restarted.

For the versions of Windows up to XP included, it was better to copy the font files inside the Fonts folder and to remove the font when uninstalled - this is the default behavior of Windows when you install fonts manually. Not doing so asked for a greater attention.

Standard Installation (Windows Default)

The standard installation will copy the font file in the fonts folder of Windows. It the default behavior when you install a font manually.
Using the Windows Explorer, all you have to do is to drop the file in the Fonts folder, and Windows will make all the activation actions automatically. Up to Windows XP included, the simple fact of opening the Fonts folder in the Explorer may reactivate all files present in this folder. (See the 'Dormant Fonts' entry in the help file of OT1 Font Manager).
When a font is uninstalled, the file is permanently deleted. You need to keep a copy of your font files if you want to reinstall them in the future.

This behavior has the advantage of simplicity. But, if you need to manipulate fonts often, it may get tedious and may lead to problems. 
For instance, if dormant fonts are present, you may duplicate font files without being aware of it and end up with an older version of a font you think you updated.

Installation As a Shortcut

When you manipulate fonts often, it may be tedious to copy font files continuously. Installing fonts as a shortcut will activate the font from its current file location.

This option offers better flexibility, but you should be aware of disadvantages it may present. For instance, if fonts are installed from a removable media, they may appear and disappear according to the availability of the support, which may lead to unstable applications.

How To Install a Font As a Shortcut in Windows

Up to Vista included, use the Control Panel, and uncheck the box 'copy fonts to the fonts folder' at the bottom of the Install dialog each time you install a font. With Windows 7 - once the option is activated in the Control Panel - right click on the font file and select the Install as shortcut option.
Using a font manager like OT1 Font Manager greatly eases this kind of manipulations.