I've used both Font Lister (the free version) and The Font Thing for years. Never had a problem.

Serious font addicts generally learn the hard way why it's a bad idea to install a lot of fonts in your system Fonts folder. Hint: when you get over some number of installed fonts (for Win95 it was in the neighborhood of 1,000), Windows starts to forget existing fonts, oldest first. Since the first fonts that were ever installed on your machine are the system fonts used for icon labels and menu entries, you can imagine that the effect is pretty spectacular.

And too, having lots of fonts installed in the system Fonts directory may lard up your applications' start-up times and memory footprints pretty severely.

Much better to put all but the most essential fonts into a set of "More Fonts" folders away from the system Fonts folder (while you're at it, you might as well sort them: serif headline, sans-serif text, handwriting, Halloween) and use Font Lister or The Font Thing to make them available when you need them.