i would refer to the following link for some ideas
Maximizing the dynamic (program) RAM memory by dragging the memory slider | Smartphone & Pocket PC magazine
otherwise, look into the possibility of creating a ramdisk (im not sure if its possible pre wm5) for your device
your best bet is to clean up your device and try to leave as much space as possible in the filestore but installing as much to your external storage as possible
jd