Are you saving all your project files on a different internal hard drive to the captured video files? If not it will be sluggish.
Best is to have 3 drives. OS & PE9 on a smaller C, Video on a large E, Projects on F.
I turn off the timeline thumbnails except briefly when I really need them. You dont really need them most of the time because they only give you a rough idea of where you are and they are the chief cause of sluggishness particularly if you are looking at a large slice of time. In case you haven't found it, it is very quick to change the number of thumbnails by clicking on the little frame icon to the left of "Video 1"
If you select the thubnail option that shows one only at the start and end of each clip this is usually all you need.
The reason it is better to have big thumbnails is because there are fewer of them when they are larger
For zooming the timeline in and out, the slider at the right is virtually instant on my old Core duo with 3gb ram. When zooming in, position the cursor first then move the slider.
I always use the space bar with my left hand to start and stop the preview, This frees up the mouse to be at the next spot far quicker.
