According to your post, I understand that a compatibility problem was encountered when trying to run The Sims2 on Windows Vista Ultimate x64 edition. If I have misunderstood your concern, please do not hesitate to let me know.
I did a research on the issue and found this is a known problem on the game manufacturer’s (Electronic Arts) side. EA suggested that the customers should run this game in Compatibility Mode.
For detailed suggestions from EA, you can refer to the following official website:
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