Long story short...Ive had VD2.5.5 installed on this computer for YEARS now and I've never had any trouble.  Today VDL isn't showing up as an option in kontakt or sibelius.  Any ideas on what may have happened or what I can do to fix the problem?

Thanks!

Have you updated the operating system, Kontakt, or Sibelius since you last used VDL? Those would be the first places to look.