Help me with my forgotten wines

[cathersides]

About 8 years ago I was given two cases of wine, Being 20 at the time I had no interest in wines and so stored them in my parents cellar. They have stayed there until today when my parents had a mass clear out and they emerged.
I was wondering firstly if they are drinkable. It is fairly damp and very dark in there but they have not been moved for a very long time, I seem to remember a friend of mine saying you need to turn over wine if it is stored.
One case is a case of Chateau Giscours 1992 Margaux and the other is a case of Chateaux La Tour Blanche 1989 Medoc. If there is anybody out there who knows these wines could they please advise me how much they are worth and if they are worth storing or drinking.

Thankyou in advance