Old French Wines

[prray]

My wife and I have a number of bottles of vintage French reds that we know nothing about. Her grandfather collected wine and since he passed away her grandmother has been giving them to us as gifts. We have bottles of Chateau Fourcas Hosten from 1979 as well as Chateau d'Angludet from 1975.

My question is simple. Does anyone here know whether these wines are any good? Are they worth much?

Thanks in advance, prray.