I've got the original BHD from 2003. I've been playing the missions and I thought I'd like to play some multiplayer on the server. Only problem is it says my game is out of date and I need to update it. If I update it do I lose all the progress I've made on my missions?
I really don't think so! I've updated loads of games and none of them have lost the 'progress'. I believe your save game profiles are stored separately and do not have any bearing on the main game files, to which the updates are applied. Ubless you uninstall/ re-install the game, your progress will not be hampered.