mabrookes: Could the second one be D?
http://en.wikipedia.org/wiki/D_%28video_game%29 Seems unlikely but thought id mention it just in case.
no it's not :( ...but another exciting game...reading through all the guesses I get the feeling I have far too little time ^.^
but seems like D isn't a very extensive game.
Lemmus: Zeeaire, I have a possibility for you on the second game. Have you taken a look at The Legacy: Realm of Terror? It's a horror adventure/RPG from 1993 which takes place in a (mostly) empty haunted house. The box cover shows an image of the staircase in the main room, so that may be the image that you're thinking of. The game isn't on GOG, but you can find an article about it at wikipedia (The_Legacy:_Realm_of_Terror), and the box art can easily be found with a Google Image seach..
I'm not a big horror game fan myself, so the only other title that I can think of is Clive Barker's Undying, and that's probably too recent to be what you're thinking of.
Hope this helps.
~Lemmus
thanks for your detailed answer :) but both of them aren't the game I'm looking for, they have different graphics/gameplay..., nevertheless both are great games, even though The Legacy it's pretty difficult...tried to play it but I failed miserably.
I guess I'll just be happy with Plague of the Moon and leave the other one an unsolved mystery to myself...
probably I just don't have enough clues for it or I have to be satisfied with the idea that I've played that (crappy) Ghostly Desire thingy. well,if I'll come across it eventually I'll actualize my post.
All of you have already helped me too much, very nice of you ! :)