There is a registry setting to fix this for WM2003SE. It worked for me, but I am on WM5 now.
Here are a couple of threads talking about it:
Axim/MobilitySite thread &
Pocket PC Thoughts thread
The "Neverdorkmemory" setting did work for me. I slid it to the setting I wanted and it stuck. I did leave a few MB dedicated for Storage in case things like temp files needed to be created.
As with anything like this, YMMV.