Sadly I already activated the key on GoG, I never even actually used the discs in my laptop when I bought it for PC. If I can transfer it to you I will, but I dunno if GoG allows/can do that.
As for Splinter Cell, I'm not really interested in the older ones cause I'm not a big stealth fan. Conviction interests me because the stealth isn't the end all be all of the game. Blacklist looks even more like a straight up action game. I don't blame people for hating the fact that stealth is going away, but I've personally been enjoying these various game series changing to a genre I like more.