How big are the images? Resolution? If the images are HUGE this will slow you down.
Project settings are under "File/Project Settings..." in the big menu bar at the top of the screen.
Do you have sound in your file?
Do you have particle effects?
Are you using any layer shading effects?
Could you post a screen grab of the layer/s or even the file itself?
Have you tried turning off some of the options in the display settings like, Transparency, smooth images, antialiasing...
Have you tried turning on "Allow Frame Skipping"?
Have you read the help file and done all the tutorials? (had to slip that one in. I'm just evil and crotchety.

)
-vern