Hello ! This is my first day on GOG, I love the idea of the whole thing but I hesitated before subscribing, which I eventually did. The first game I bought is Messiah, one of my favourites games : in fact, I already bought it a few months ago on CD format. The version I have strangely had no audio CD with it (White Label Edition) and consequently there were many audio files missing. Plus it was hard to make it work. I managed to do so, but without musics, no sound during movies and random crashes during the game... Talk about gaming experience ! After a long hesitation, I finally bought it on GOG because it was apparently compatible with XP and Vista...
Firstly, it doesn't work at all on Vista 32b (it's a laptop, Toshiba A300) : the setup runs fine, but when I try to launch the game, there's a little screen asking me to choose the resolution. Whatever is the choice I make, well, nothing happens ! When I try again, it says (not exactly) "Previous shutdown didn't succeed, please reboot and try again". I did it, but nothing new... So I took a look on Messiah's forum but no one seems to have this problem, and that's a bit frustrating...
Then, I tried to install it on Win XP (were I installed my first version of Messiah). After deleting the first one, the "GOG version" installed well, same resolution screen, "ok"... It works ! I even have sound during the movies and during the game. But my joy didn't last for long. After half an hour, the music started to become kind of "scratchy" at moments, but I decided to do with it. I managed to fight my way to the lab were the Prime Father is killed, and I was really waiting for this because on my first version, there was no sound when Satan and God talk to Bob (and at this point I had no idea about what was going on, did Satan lured Bob ? Does God blame Bob for what he did ?). And during the key scene, there is sound, but it is "over scratchy" and I can't hear a thing at all... I was like : -_-"
So, does anyone had/have the same problemm and a possible solution ? It's a bit frustrating to buy a game that doesn't work well, especially when it's the second time you buy it (ok, the price is interesting but it ain't no excuse). I just hope that all the games on GOG aren't as buggy as this one :-/
PS : I'm french, so please excuse me if my english isn't always correct :-( Also, I hope there will be other languages available for GOG, I can play games in english it doesn't bother me (original versions are always better) but it could be an interesting idea :-D

Have you tried changing the sound hardware acceleration on your windows xp machine?
To do so just go to your start menu -> run -> type dxdiag and hit enter. Then when that loads up go to the sound tab and it will have a sound hardware acceleration slider. Try lowering it at first and running the game and if that doesn't work try setting it to off on the slider and run the game again.

Thanks for the quick response!
However I did what you said but the problem is always there. I noticed something really strange : sometimes, when I don't move my character, the music doesn't work well (the "scratchy" sound, I can't find the word, I don't even know if it really means something). But when I start running around, it works perfectly ! ... And if I stop running, same problem :-S
I'm playing with a gamepad, I'm gonna try to play with the keyboard and mouse but I don't think it is the solution...
EDIT : tried and didn't change anything... I also tried to change several in-game sound options but didn't work neither !
EDIT 2 : I also noticed that when the music is scratchy, if I press CTRL+ALT+DEL, I go back to the desktop but the music still plays... perfectly ! But when I try to go back to the game, same problem again (+ the screen is dark). If anyone knows how to fix that, I'll be very thankful !
EDIT 3 : I finally decided to fix half of the problem in my own way lol. I downloaded the soundtrack of the game. Then I opened the files in WMP, put the list in "random" and "repeat" mode, launched Messiah, turned-off in-game music, loaded my savegame and played the soundtrack by pressing the "play" key on my keyboard. It works well and no more problem with the music (hey, the music even stops by itself when going to the in-game menu). However, there's always the problem with the voices but I guess I have to roll with it...