Some applications are preloaded on startup. This means when the Zaurus starts up, they are automatically loaded into memory. This makes them load very fast when you run them because they are already loaded. However, because of that, they also use up memory.
You can prevent them from preloading and conserve memory by disabling the preloading flag for each of the preloaded applications. To do that, tab on the application icon and hold the stylus there for a few seconds and a properties screen will appear. Untick the option "Fast load (consumes memory)".