No, with Pocket PC 2003 SE, there's no way to set all available RAM as program memory. Windows Mobile 5.0, however, is designed to allow this. Many people have had problems after upgrading, so I wouldn't go this path. Instead, try to maximize as much program memory as possible by installing apps to BIS or your SD card, moving DLL's, etc. My X50v uses up only 8 megs of program memory for storage.
Also, read
this Aximsite tutorial on memory management.
alan