I upgraded from 5 to 11 some years ago - and found minimal changes - wondered why I bothered as in my world it was quite expensive.
I would thus agree with Paul - if you have, or can find a version of 5 it should suit - there may be a problem with backward compatibility, but could probably be handled via gedcom conversion, if nothing else.
I haven't used vista, & you have given me another reason to stay with what I have for the time being.
Trish