What operating system do you use and how much memory do you have?
If you're on Windows, you can right-click My Computer and select Properties to find your system information. You can also launch Task Manager to analyze your system's performance.
Thanks for your reply. In the properties window, it says I have 2 GHz and 2GB od RAM. I'm running Windows XP Professional. I haven't been able to find the requirements for running CS4.
Okay, 2G memory is pretty good.
A program takes up a certain amount of memory, but so do files, and a 10Mb file, loaded into Fireworks will require more than 10Mb to be worked on. I'm still on CS3 and my files tend to be smaller. However, there are some things you can check to rule out your system.
Start Fireworks (without a document open)
Right-click on a blank place in your task bar and launch the Task Manager. Click the Performance tab (you'll get a graph).
Switch to Fireworks and open your document. If the CPU Usage in Task Manager pegs at 100%, then you really do have a memory problem. What happens is that Fireworks has to use part of your disk drive as additional memory. Moving data to and from the disk is a slow process and there are circumstances that can make it slower.
(You might also click the Processes tab. My Vista machine has 30 processes running, but right now I'm only running Chrome and Outlook. If you have more than 40 processes in your list, you may have unnecessary processes that use up system resources. Browser toolbars and malware are common culprits.)
Other things to check would be your hard drive space and your disk fragmentation. From Windows Explorer, right-click on your drive (for example, C: and select properties). If you don't have much unused space (the pink area in the pie chart) then you are running low on disk space. For nice instructions on how to clean off some unnecessary files and check your drive's fragmentation (and how to defragment your drive, if needed), see The Elder Geek:
Also, you should read about the pagefile
http://www.theeldergeek.com/paging_file.htm (multiple pages from this intro page) If your pagefile is small, you might be able to improve performance by increasing its size.