I've run the stand alone versions of Geneforge 1 and 2 on XP just fine in the past. When the entire series came to Steam, I decided to get the whole set. However, these versions of the games run at a less than satisfactory pace, with Geneforge 3 being especially slow. Moving the mouse around is jumpy in that "system playing catch up" sort of way, and bringing up the menu takes around 20 seconds, and basically hangs my system until it appears. I don't have access to my registered stand alone copies of 1 and 2 anymore, so that's a bust. Strangely, the title screens function just fine, it's only when I get in to the game proper that the problems appear.
4 and 5, on the other hand, run just fine, but I'd like to play the games in order.