Who are the oldest noble (non-royal) family in europe that's still around?

Question

Who are the oldest noble (non-royal) family in europe that's still around?

Answer 1

I believe the Massimo are the oldest.  Their family lines can definitely be traced back to the early first melennium.

http://en.wikipedia.org/wiki/Massimo

The Habsburg are another.  

http://en.wikipedia.org/wiki/Habsburg

The Orsini

http://en.wikipedia.org/wiki/Orsini

The Colonna

http://en.wikipedia.org/wiki/Colonna

The Medici

http://en.wikipedia.org/wiki/Medici

Almost all those people bearing the title "Prince" in Italy are nobililty not royalty but that is no skin off their nose as many can trace their families back before many royal houses.

Americans have a tendency to think anyone who bears the title prince is royalty.  Prince Lorenzo Borghese, I understand, told interviewers more than once that the Borghese are nobility not royalty but still  publicist continued to refer to him as royalty.  He is a direct descendant from James II of England but that far back doesn't make you royalty.  

Answer 2

The Medici and Hanover houses are probably the best documented. Of course, if you're technically speaking, all families are the same age because we all go back to the same common ancestors. It's just a matter of whether you're researching surnames or just proven lineages.