I have the mac version of sims 2 and several expansions. I also have windows 7 installed on the same computer using parralels desktop v5.

I was wondering if it would be possible for me to somehow use the windows only expansion packs (apartment life, freetime) w/o buying all new games and other expansion packs?

Thank you!

No you cannot use your OSX version of the games in windows and you cannot use the windows versions in OSX. While I've heard Parallels works better now with games, you still probably wouldn't like the lag it will produce. Since you are effectively running two OS's at the same time, and having to share all your system resources between those and the game.