Yes as far as I have see the installation of Bon Voyage keep the Downloads and the rest (neighborhoods...). I don't understand why. :roll: But yep, a save before installation is always useful.
Have you a Nvidia graphic card ? With it, I had a D3Derror when suddenly the game ceased to answer and crashed (despite of reinstallation). Now I haven't such a card but I've read that there is a patch for Nvidia users with Sims 2 problems.