Troubleshooting - Muvizu runs slowly

If you want to improve Muvizu's performance without upgrading your PC there are a few ways which you can do this:

Ensure all graphics drivers are up to date
Make sure that other resource-intensive programmes are not running at the same time - things like virus scanners, photoshop, modelling packages and games can drastically affect system performance
If you are on Windows Vista or newer then try using the basic themes, to reduce the load on the graphics card

Run Muvizu in DirectX 9 mode (File>Options)
Run Muvizu in unlit mode (Hit F12)
Reduce the number of objects and characters in your scene. For example if you build a city and you only film a 1 character on 1 street then delete everything that can not be seen by the camera view. Save the complete set separately for future use.
Reduce imported videos and audio tracks. If you import a video for clouds moving across the sky, you can remove that from your scene until the last minute before you render your video. If you have a 10 minute scene but you are only recoding a 30 second section of that scene in a SET file, then edit your audio to only include the 30 seconds you need for that part of your video.