Bought and installed Seasons, Sims is now crashing every 5 minutes ):

Could you post the DxDiag part about your graphic chip. Might be below specs.

You can try lowering your graphic settings and turn of mirror reflections to see if that helps.

another option is to try the factory reset described in this post: http://answers.ea.com/t5/The-Sims-3/FAQ-Troubleshooting-Steps/td-p/714/