When I first started to use Flash CS3 in Vista I noticed that all of my flash movies were performing very very slowly.
Honestly .. I'm not sure why. But, here's how you can make it perform better.
- Navigate to your Program Files -> Adobe folder(s) -> Adobe Flash CS3 and find the Flash.exe.
- Right click on that file and goto the Compatibility tab.
- Check "run this program in compatibility mode", and voila, suddenly it's running as fast as it did on XP. Happy coding!