If you still have GK1 and are interested in replaying it to its conclusion, I would recommend using the custom installer at SierraHelp.com. It should take care of any pesky bugs (most of which are likely to result from compatibility issues with newer machines).

I also strongly suggest playing through GK2, but be warned that the interface is way more restrictive than that of GK1. IMO, this is the game's biggest weakness, as the storyline is extremely good. FMV, in hindsight, was really one of those ideas that worked better on paper than in execution.