MysterD: The thing w/ Achievements for me is: they should be built into the game itself for offline play and offline profiles. GOG, Steam, Games For Windows Live, PSN, XB Live - those Achievement systems won't be online forever sadly.
And of course, if offline - I should have an option to Reset the offline Achievements popped or not...b/c sure, why not?
AdastAdamov: Actually there are options when you use Steam emulators - achievements can be unlocked offline. Though you would have to use Achievement Watcher (or other tool) to see them.
And there is also a tool that allows to unlock/lock achievements
online on Steam, which is needed if you want to reset them and try 100% game again.
Helpful answers, thanks! And, hey, since you seem a bit knowledgable about Achievements, you wouldn't know if there's a way to transfer Steam's to Gog's, over a single identical game of course, would you ?
I finished Metro 2033 at 100% through Steam, years ago, and was wondering if that record could be imported...