Hi, I just joined to say that a very old (circa 1999) but very useable beta version of the aforementioned Munsell Conversion program is still available here:
http://web.archive.org/web/20020809130910/standards.gretagmacbeth.com/cmc/munsell.exe
I've only tried it under Windows XP, but it worked fine for Munsell to RGB and vice versa. Best of all it's free and there's no death clock :)