An interesting side effect of the font preview window on Windows XP and earlier was that, in order to display a preview of the font, it installed it temporarily for all applications to see and use. While the preview window was open, you could use the font in any other application (including DTP ones). This was a nice solution for those cases where you quickly needed to create some ad or client work requiring a specific font but you didn't want to install it permanently. However, this side effect of the preview window was removed in Windows 7.
Because this feature (even if it was considered an unintended side effect in earlier Windows versions) was quite comfortable for many who learned to rely upon it, we wrote a small and simple utility to reproduce its behavior on Windows 7. The utility can be downloaded in a .zip archive. Just start the executable inside (you can copy it into any folder you prefer or add a desktop shortcut to it). You can either supply a full path to a font file on the command line (which makes it possible to assign it to a particular font file extension) or, if started without a font file specified, it will allow you to browse for one using the usual file open dialog.
The program requires the .NET Framework 2.0 but as it is supposed to be useful on Windows 7 where this framework is part of the system by default, you won't notice anything.